Portuguese tinfoil hat on:

Columbus was a Portuguese plant meant to distract the Spanish from competing in the African route to India, that's part of the wrongful insistence on them being "Indians".

Other things:

-Most of the names he gave to new found land were names of villages close to his hometown of Cuba, Alentejo (south of Portugal). Portuguese Cuba was called Cuba since at least the 13th century.

-He wrote in Castellan with typical errors of Portuguese natives.

-The papal bull regarding his travels write his name using exclusively Portuguese accent characters (the ~)

-In his early days, he married a Portuguese noblewoman from Madeira and lived with her there (very far from his supposed hometown where the names come from), something very hard to achieve if he was actually just a Genoan wool weaver.

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Some other theories say that he actually wanted to go to America, and was refused by the Portuguese king, and that's why he went to the work for the Spanish.