The First Crusade wasn't really a disaster - the Kingdom of Jerusalem that it created lasted for nearly 200 years (even though for much of that time it didn't actually control Jerusalem). However, it was by no means a cakewalk. The crusaders were always within a hair's breadth of being defeated by the (much larger) Muslim forces, and at one point they were saved from defeat by a "literal" Act of God - while the Crusaders were trapped inside Antioch and slowly starving to death, a priest claimed to have received a vision that the Holy Lance which pierced Jesus' side was buried underneath a local church. The crusaders actually dug into the foundations of the church and found a piece of iron that resembled a spear head, which boosted morale so much that they charged the Muslim armies encircling them, catching them off-guard and defeating them. The Fourth Crusade was also (debateably) a success, depending on whether or not your name was Enrico Dandolo.
The problems that plagued the Middle Eastern Crusades can mostly be attributed to the massive distances that had to be traveled - having to travel from Western Europe to the Middle East essentially on foot was a pretty grueling endeavor, especially given that everyone involved was expected to live off the land as they marched. The complete lack of anything resembling a supply chain wasn't as much of a problem when conflicts were confined to Western Europe, but it led to mass starvation and the virtual elimination of cavalry among the invading armies if taken too far. In addition, some crusades were decided by sheer chance. The Third Crusade failed when the Holy Roman Emperor, the most powerful ruler in Europe at the time and one of its most gifted military leaders, drowned during a river crossing. This left the Crusader armies in chaos and disarray, and, while other leaders stepped up to replace Frederick, they were ultimately defeated.
The crusades that took place within Europe, such as the Baltic Crusades against the pagan Lithuanians and Prussians, were far more successful and led to the creation of stable nation-states that lasted for centuries, so there obviously wasn't any inherent problem with the idea of crusading.
You should read Asbridge‘s „The Crusades“. It covers all crusades and should give you the information you are looking for.
Anyway: First and foremost, the crusades were not “all such disasters”. The First Crusade was arguably the most ambitious and difficult European military expedition done in the 11th century. And against all odds it was successful. The 3rd Crusade restored much of the lost territory of the Kingdom of Jerusalem. The 4th Crusade captured one of the largest cities of the world. The 6th crusade recaptured Jerusalem. The Reconquista was a complete success and the Northern Crusades projected German hegemony into the Baltics. (For clarity’s sake, I am not a crusade-fan. I just want to point out counter-examples.).
These successes were all the more stunning, when you consider the challenges the crusaders faced.
The distance. A crusade could take several years and communication was greatly delayed. During the 3rd Crusade, this became very important for Richard I (The Lionheart), as things in England spiraled out of control when his brother tried to seize power. Richard was just gone too long and the troubles back home distracted him. If it had just been a small frontier war in France, this would not have been a big issue as he would have been gone only for a few months and never been out of convenient governing distance. Another topic is logistics. Supply-lines in the Middle Ages were hardly worth their name, but during the 1st Crusade there just weren’t any. The crusaders were overjoyed if they found Italian ships off the coast, but otherwise it was foraging. Starvation was a very real threat for them.
The unfamiliar climate/diseases. Richard fell ill during his crusade. This could of course happen in Europe as well (e.g. to his relative the Black Prince during his campaign in Spain), but the unfamiliar climate/diseases/food were certainly not beneficial to a crusader’s health.
Unfamiliar enemies/tactics/terrain. Aka Horse archers and Anatolia. While many crusaders coped with these problems (e.g. the 1st Crusade), some did not. Also, during the 1st Crusade during the siege of Jerusalem the crusaders had trouble finding enough wood to build siege engines (they took apart some Italian ships to build them, eventually). This problem would have been unthinkable in Europe.
Europe-wide coordination/Lack of central organization. Most crusades were European endeavors and not just limited to single kingdoms. Coordination on such a massive scale could take years to come to fruition and then the results were uncertain. One of the major reasons why the 4th Crusade was diverted was that much less crusaders showed up in Venice than had been anticipated. On a smaller scale, this problem does not arise that starkly, e.g. in one kingdom there is a good chance that all important decision-makers know each other personally. Also, there were inevitably tensions between the different monarchs. The most famous example is probably the rivalries during the 3rd Crusade. Such rivalries also occurred in regular campaigns as well, when lords strove for glory or tried to settle scores, but usually there would at least be some single highest authority (e.g. the king) who could mediate. Many crusades never managed to find that central authority.
Religious zeal. This sound odd, as usually you would want your soldiers to care about the war’s success, but in the case of the crusades it was sometimes detrimental. Richard toyed with the idea of attacking Egypt instead of Jerusalem, thus cutting off Saladin from the base of his power and drawing him further west. Jerusalem would be the next step, once Saladin was defeated. He reasoned that a direct attack on Jerusalem would be almost impossible. The crusade’s soldiers, however, had dedicated themselves to recapture Jerusalem (and not Egypt) and would not be diverted so close to their ultimate goal. The crusades’ initiators were often torn between on orderly but dispassionate crusade and zealous but potentially chaotic crusades. During ‘secular’ campaigns you just had your bands of mercenaries and feudal warriors, who had no intentions of rushing the attack.