Columbus was an Italian who's history was written by vindictive Spaniards. It was in their, the Spaniards, intersts to discredit Columbus in the eyes of the Spanish monarchs.
Hmmmm.
He'd worked earlier for Rene d'Anjou, cousin of the King of France and, as it turns out, grandfather/uncle to both Isabella and Ferdinand, and, later on, Elizabeth of England. Rene's brotherinlaw was King of England.
No doubt Columbus was looked at with great suspicion by many Spaniards!