I've read that Columbus, far from having some insight that no one else did about the nature of the earth, actually believed the Earth was smaller than it actually was at a time when its size was quite well established. In other words, everyone else was right, not him.

So how, then, did the positions come to be reversed? How did Columbus go from being lucky and deliberately misinformed (in that he refused to consider other arguments) to being the only person who understood the way the world really was?