If someone does such a good job as president as to gain the votes of the majority of citizens democratically multiple times why shouldn't they be able to go more than two terms? What reasons or justifications did congress have when creating the 22nd amendment?
The 22nd amendment was basically pushed by the Republicans almost immediately after Roosevelt's death and the surrender of Japan. The reason why it wasn't pushed as hard before was because during Roosevelt's terms, he was fairly successful and it was a time of international crises so the US did need to maintain a very strong head of state on the global power.
The reason was to codify the traditional two term honor policy that most presidents followed (although some ones did try, like Teddy Roosevelt). The purpose for the need of this amendment, supporters argued, is to limit any one person from getting too much power. And it'd be hard to deny the influence of Roosevelt, Supreme Court, policies, laws, executive orders. By being in power for essentially one additional term than other presidents before him, and during a time of depression and war, Roosevelt did have tremendous political power.
The Democrats also did sign off on this because they did not wish for a republican to have this amount of power in the future.
The 22nd amendment is ultimately just one additional check on the presidents power to prevent any one person from becoming too powerful.