Republicans and the voters that voted Trump are definitely the stupider part of that situation. Being fooled by a fool makes you pretty stupid. Failing to detect the blatant lies of a pathological liar makes you stupid. Thinking the obvious flaming sociopathic narcissist is on your side makes you stupid.
The only way to be that stupid is by a lifetime of indoctrination that up is down. Americans have been indoctrinated for a century that freedom is the ultimate highest value, higher than life itself, without ever actually making a good definition of what freedom is! And Trump is a sociopathic narcissist, with no conscience no respect for anything or regard for other people and little self control, and that is seen by most of the American population as the ultimate expression of the freedom they idolize.
Americans are also indoctrinated to admire being rich, as a sign of skill and intelligence. And since Trump is rich and famous, Americans think he is intelligent, despite his fortune is based on his inheritance.