Was Christopher Columbus most likely "crazy" or a terrible navigator if he originally thought he was in/near Asia or India, but really he was in the Caribbean? How does he make the mistake of traveling so far and not realizing this? Poor navigational skills? Craziness? Curiosity?
As I addressed in these two previous answers, he considerably underestimated the size of the earth, so believed that the circumference of the Earth would have Asia being, if traveling west, much, much closer than it really was.
A popular theory was that he was Portuguese, working as spy/inner agent for the Portuguese King and ordered to misdirect the Spanish about the true route to India.