>>27606111Realistically, it's a common thing on islands, especially in the tropics.
Kanto is a harsh environment where every advantage would matter, and with the massive amount of poison types, a species getting more intelligent (psychic) every generation would be a massive boone.
Whereas on an island, it might not even be needed. Many tropical, island species, are for a lack of a better term retarded for a lack of a better word and they fill incredibly specific niches and have little fear of predators.
tl;dr there's no reason to be that smart on an island where there's plenty
