The people that knew (cartographers, cosmographers and the like) realized he was wrong and told him as much. Between 1486 and 1487, a group of scholars held commision in Salamanca and Córdoba and turned down Columbus' project as unviable.

Columbus responded by writing back to Portugal, sending his brother Bartolomeo to England in 1488, and seeking the support of several Castilian nobles in the Catholic Monarchs' circle, like the Duke of Medina-Sidonia and Cardinal Mendoza. The most important of these contacts was Luis de Santángel, royal scribener and financer and one of the richest men in Spain, who backed the project with a resoning as simple as sound: If Columbus was wrong, the loss would be little and affordable, while if he was right, the riches brought by his route would be unimaginable. It would be on Castile+Aragon's interest to have that route in their control, if it turned to be real, than in a rival power's. All this support (by Santángel and, I stress, many other people) translated in a new audience with the Queen in 1489 where she only agreed to "re-study" Columbus' project after the fall of Granada.

At that point the Christians were making quick advances and Columbus though that the matter would be solved in a few months, but in 1490 the war became stationary. By 1491 he run out of money and returned to La Rábida monastery, where he had been given asylum in 1485, and began to make preparations to sail for France. The story goes that the La Rábida monks reached him with the news that the Court had approved his project and conditions when he was already on the road to port. The thing that finally convinced the Crown to accept Columbus' project and demands was Santángel's offer to loan the money necessary to launch the expedition to both Columbus and the Crown.