According to most historical textbooks Columbus made mistakes while measuring the size of the Earth. This led him to believe, that he can travel to India westwards in a reasonable time. This is however quite strange, that he let no one correct him in his mistake.
Could it be possible and was it ever considered by the historians, that Columbus was simply lying that he can find the way to India? That he knew about existence of Americas somehow and used the lie to get funding for his operation?