They were right to laugh at Columbus. He thought the world was 3x smaller than it had been known to be for more than 1000 years. He was lucky he found the new world instead of starving to death halfway to India.
He probably didn't think that, but could not sell his project without getting potential investors to believe it. (At the time, nobody knew exactly how wide Asia was, although travel time on foot showed it was not as big as it would have to be.) Things haven't changed so much.
But he continued insisting, to his dying day, that he had reached Asia.
