The problem is that it's not a question of intelligence.
Trumpists and their ilk are living in echo chambers of "alternative facts", perpetuated by Fox News, Murdoch newspapers and an nearly endless amount of rightwing influencers (starting with Rogan at the top). They are not looking at what's happening, because they are surrounded in a very comforting bubble of disinfo and propaganda that confirms everything they wanted to hear: The illegals get deported, the queers get finally put in their place, the liberals are frothing with anger, finally men are back in charge who tell women where they belong and America is going to be "great" again any moment now.
It's fascism and fascism has always been a "cult": The early pioneers of fascism (particularly D'Annunzio and later Mussolini) explicitly said their aim was to create a "secular religion" around the nation, the people and the leader. And you can only be a member of that religion if you accept its "truth" and reject everything that contradicts it.
Very smart people can adhere to a religion for a variety of reasons and the most obvious one is (and always has been) because it promises them power over others.