There are a few reasons why Carter is typically considered to be a bad president, at least if we're assuming that "bad" in this case means ineffective.

After the Nixon and Ford years, Americans came to view their government as being coldly pragmatic but, more importantly, corrupt and incompetent. Moreover, in terms of international affairs, the U.S. was encountering an international system that was becoming increasingly multi-polar. In other words, global power was shifting away from the two superpowers and disaggregating among the Third World states, Asia, and an increasingly integrated Europe. This disaggregation of power was most clearly symbolized by the U.S. defeat in Vietnam and a series of oil crises instigated by OPEC (a conglomerate of oil producing states based in the Middle East, in addition to Venezuela) that made gas prices soar in the U.S.

Carter believed that he could simultaneously renew America's trust in government and reassert America's leading role within global affairs. He failed in both regards.

A lot of it had to do with his personality. He came to Washington believing that he could change the way politics was made. He hoped to make politics more transparent which would, he believed, make politics more effective and less divisive. Perhaps unsurprisingly, Carter's self-perception as a reformer and Washington outsider concomitantly carried what can best be described as a savior complex. He looked down on other politicians, believing his deep-seated morality made him the only one capable of bringing the Washington establishment into line. Thus, Carter arrived in Washington expecting Congress to fall lock-step behind his policies. Naturally, congressmen from both parties weren't to fond of the way Carter handled congressional relations. This tension between the executive and the congress was exacerbated by Carter's aides, who were primarily old friends and staffers from when Carter was governor of Georgia. Georgia politics are, of course, nothing like Washington politics, and Carter's aides were woefully inadequate for the job. Still, he kept them, much to the chagrin of even the Democratic congressional leadership. Due to bad congressional relations, Carter had difficulty passing domestic reforms on such major issues as social security and health care. If this wasn’t enough to derail his policy-making process, Carter’s hands-on approach to everything didn’t help. He was notorious for wanting to personally review and authorize even the most minimal of tasks, going so far as to personally OK each morning who would be allowed to use the White House tennis courts. Not all of the problems with Congress stemmed from Carter's and his aide's personalities though. After Watergate, politicians promised to make politics more transparent. This, unfortunately, made it more difficult for politicians to do the back-room bargaining that leads to compromise and, eventually, the passage of legislation. Moreover, Congress as an institutional structure was changing. During Carter's presidency, Congress split into many different caucuses (basically, groups of like-minded congressmen that ally to create mutually supported policies). These caucuses existed, like always, at the broadest level (Democrat and Republican), but now there were additionally a plethora of smaller caucuses like an African-American caucus, a women’s caucus, regional caucuses, etc. This explosion of caucuses allowed almost all congressmen to gain good committee assignments. Congressmen used these congressional committees, covered intensely by the media, as ways to generate publicity and gain support for re-election. Due to the greater publicity that even junior representatives now held, there was less of a need to rely on their party label when they ran for office. Instead, they could run on personal recognition. All of this ultimately meant that there was less of a need for individual congressmen to hew toward the party line, which made it even more difficult for Carter to gather congressional support for his policies.

In terms of foreign policy, one of Carter's strengths in the 1976 election was that he rejected the Nixon Administration's idea of realpolitik, which held that the international system did and should operate solely on the rational calculation of self-interest. Carter instead believed that the United States should frame its foreign policy within moralistic terms, and early in his administration he made human rights the top priority of U.S. foreign policy. In reality, this didn’t happen. Instead, he relied on traditional Cold War conceptions of world affairs centered on national self-interest. After the shah of Iran, who had brutally repressed the Iranian people for decades, was overthrown during the Iranian Revolution, Carter allowed him to come to the United States. (The Shah was suffering from cancer; Carter allowed him to come to the U.S. to receive chemotherapy). In what is probably a huge understatement, this didn’t sit well with most Iranians. Soon after, the U.S. embassy was overrun and the American staffers there were held hostage for 444 days. Every day that the hostages remained in captivity showed America’s apparent weakness on the world stage. It didn’t help with all of the news outlets reminding Americans at the end of every broadcast that “Today is day [7, 84, 300, etc.] of the Americans’ captivity in Iran.”

To free the hostages, Carter attempted a night-time raid by American special forces. A U.S. plane landed in the Iranian desert carrying stuff for the raid and soldiers. A handful of helicopters carrying more soldiers was coming to meet at the makeshift air field when one of the helicopters flew into the plane, killing many of the Americans. Needless to say, it was a big embarrassment and only seemed to further prove America’s weakness on the world stage. Iran wasn’t the only foreign policy problem Carter faced. In addition, the Soviet Union had been making great gains in the Third World, particularly in Africa. Thus, it appeared that not only was the United States becoming weaker, but the Soviet Union was becoming stronger. This fear of increasing Soviet power culminated with the Soviet invasion of Afghanistan in 1979.

All of this was compounded by the worst economic crisis in the U.S. since the Great Depression. Carter, no matter how correct he may have been, didn’t exactly instill confidence in the American people. Regarding what appeared to be unending inflation, he told the public that all he had to offer were “partial remedies.” In the face of a rate of inflation in the double-digits, he asked employees not to increase their wages by any more than 7%. It also didn’t help that in general, Carter wanted to deregulate most government agencies. Thus, when many people were calling for some sort of government intervention, Carter was cleaning out many federal agencies.

All of these problems, foreign and domestic, appeared to show an ineffective president. At one point, Carter tried to show that he was being an active leader by asking for the resignation of his entire cabinet, who dutifully complied. Instead of showing action, however, the American public believed the act only proved that Carter could not at all manage the presidency. Not all of these problems were Carter’s fault. The economy was doing poorly when he came into office and it didn’t start getting better for a couple of years into Reagan’s presidency. Nor could he change the way post-Watergate politics was conducted. But his refusal to work with others, his need to oversee even the most miniscule of matters, and his inability (or unwillingness) to carry out a foreign policy that adhered to U.S. moral sensibilities and national interests, really did make him one of the least effective presidents of the twentieth century, certainly of the post-WWII era.

EDIT: I stated that Carter's entire cabinet resigned, which was incorrect. Five resigned: the secretaries of the Treasury, Energy, HEW, and Transportation, as well as the attorney general.

EDIT: It was mentioned that I left out the energy crisis. Here's a brief summary: Foreign oil prices had been rising since the early 1970s while U.S. reliance on foreign oil was simultaneously increasing. While a problem throughout the 1970s, it became particularly bad in 1979 as OPEC continued to raise oil prices. Gas shortages ensued. People began waiting in lines to get gas. Other people, seeing the long lines of cars waiting for gas, thought that they needed to get in the line and get gas before it was all gone. The lines got longer. Because there were so many people getting gas, people tried to get as much gas as they could. Since everybody was spending money on (really expensive) gas, it drove down the amount of spending in other sectors of the economy, making deflation worse. Simultaneously, because everyone was buying gas, oil prices continued to increase since such high demand only led to even further inflation. Everyone blamed Carter.

Just to be clear, historians rank Carter below average, but by no means among the worst presidents. Among 44 presidents, the aggregate of historian rankings put Carter at number 27, in the third quartile. Among recent presidents, Carter is ranked ahead of George W. Bush and Richard Nixon, and is one rank behind Gerald Ford.

Source.

I'm not going to address the largest claims of Carter being a terrible President that you already addressed, and instead I'll bring up a point I have come across as to the more underlying reasons why he is seen in this light by so many.

Jimmy Carter was seen by many at that time as being too cautious and feeble as a leader. Remember, he was President during the Cold War, and with LBJ, Nixon, etc. America was used to leaders who seemed to have a decisiveness about them. For instance, one thing that hurt him was during a debate with Reagan and a question about nukes. Whatever his intended answer was, it came off like he was seeking counsel from his daughter regarding nuclear weapons.

There's a school of thought that believes American presidents derive power from acting. In the case of Carter, when the hostage crisis happened, he employed a philosophy of waiting it out. The crisis captivated American imaginations and the news made it a huge deal. Carter insisted on sticking to diplomacy and not intervening militarily. The public viewed this as indecisive and weak. When Carter authorized Operation Eagle Claw, even though it failed, his approval ratings actually initially increased. However, as time dragged on, his perceived inability to act made him appear even more weak. It ended up being the right choice, as the hostages were freed eventually but it had already destroyed his presidency by that time. According to Howell "It was Carter's failure to act - even when no obvious course of action presented itself - that ultimately proved to be his downfall...It is ironic that Carter's lasting legacy of weakness stems from his inability to take strong action in a situation that was largely out of his control."

A similar situation happened to Bush when he flew by Katrina without landing Airforce One. If he had landed the plane and surveyed the situation, he would have brought no lasting change to the situation and would have probably made it worse by making a new logistical nightmare. However, his flyby came to represent his "flyby presidency" and his approval ratings never recovered. Unlike Carter, this happened in his second term.

Additionally, Carter was a well known micro-manager, and felt that instead of having advisers advise him on details that he learn the minutia himself. This hurt his ability to see the big picture, as well as multitask.

Sources: Thinking about the Presidency: The Primacy of Power William G. Howell and The American Presidency: Origins and Development, 1776-2011 Milkis & Nelson

Should the question be restated? Why was the Democratic Party such a mess in the last half of the 70's?

They had control of all branches of the government with a super Majority in 76-78

A review of the legislation of the 95 and 96th congress seems to show a lack of focus on domestic issues. Should the Democrats in leadership positions be judged as well?

• Robert Byrd
• Edward Kennedy
• Tip ONeil?

Did the personalities of these men make Carters presidency unsuccessful?

Other commenters have given sufficient answers to your question. The bad perceptions of Carter's leadership has a lot to do with the Iranian revolution and hostage crisis, the collapse of detente with the Soviet Union and beginning of the "second Cold War", the energy crisis, and low growth, high unemployment, and high inflation in the economy. Basically, bad events were happening during his presidency and the public didn't see him as effective. I will give a counter argument as to why I think Jimmy Carter was a very strong president when we look at his policies in retrospect.

On foreign policy: He elevated human rights to a national interest of the United States. He officially recognized the People's Republic of China. He established the Carter Doctrine in the Persian Gulf. He supported the Mujahideen in Afghanistan. He transferred the Panama Canal Zone to Panama. He brokered the peace treaty between Israel and Egypt. He concluded an (ultimately fruitless) second round of arms control talks, SALT II. His national security advisor, Zbigniew Bzrezinski was one of the great Cold War strategists along with Henry Kissinger. There is plenty of continuity between Nixon and Carter particularly on the strategic opening with China (and between Carter and Reagan who continued the war in Afghanistan, the first Bush who executed the Carter Doctrine in the Gulf War, Clinton and Obama who flirted with humanitarian interventions and pursued peace between Israel and Palestine..)

On domestic policy: He appointed Paul Volcker to the Fed to end stagflation (hiking interest rates worked by the early 1980s), he challenged the country to collectively confront the energy crisis (we didn't and are living with the consequences, but you could say the private sector and Obama administration are now assembling a patchwork energy policy), he established the Department of Energy, the Department of Health and Human Services, and the Department of Education, and whether you think it was the beginning of a bad trend or not, he began deregulation, focusing on the transportation sector.

From a bureaucratic politics perspective its one thing to run as an outsider and its another thing to be one when you get to DC. Carter didn't heed this message and few if any in his administration were Washington insiders. (Halperin and Clapp, Bureaucratic Politics and Foreign Policy). The reason the Carter administration stumbled is that it had no connection to Congress, it was totally isolated from the legislative branch and therefore had trouble getting its policies passed or accepted by Congress.

There is an anecdote from Tip O'Neil that shows his poor relation with Congress. After the election Carter invited Democratic leaders to the White House for a breakfast and served only coffee and biscuits. O'Neill took one look at the spread and said "Mr. President, we won the election."

Any historians care to share their thoughts on The October Surprise? It's been three decades. Granted, by its nature, it is hard to definitely prove, but Reagan's subsequent, proven aptitude for cooperating with Middle Eastern "terrorists" during the Iran/Contra scandal suggest for the observation that one of his campaign managers, William Casey, interceded in untoward ways.

Related, how reliable do historians view Woodward's Post-Watergate books? Is his claim regarding Casey's deathbed confession seen as essentially true?