Columbus knew he wasn't in India, but he lied for money

"The documents confirming these privileges confine the Admiral's realm only to "the Ocean Sea in the region of the Indies"[19]. Therefore, if the newly discovered lands were not really in the region of the Indies - that is, in Asia - Columbus's entire fortune may have been at risk. Indeed it may have been just such a thought that led the Admiral to demand that the crew of his second voyage sign a document swearing that Cuba was the mainland of Asia[20]."