I actually believe he's just plain dumb - he's never had to improve himself and wasn't too bright to begin with. But he has something that is hard to come by.

That culty gift of gab. He utterly captivates huge swaths of people with just his speaking cadence alone. Granted, he's not captivating them because there is any actual substance to his words. But people are dumb as dogshit. That he has money and peripherally gives lip service to supporting their political causes is really only secondary. He speaks to them and it's impossible to not notice it.

That shit is worth gold. Note that everyone is pretty much in agreement that if he dropped dead tomorrow the cause would suffer a potentially irreparable blow, because there isn't anyone else in the party that has what he has. Very, very few people do. Anybody think Don Jr. could pull that off? No fuckin' way.

So Trump is extremely valuable right now because he is able to get all these people to turn off what few critical thinking skills they possess while the party's powers-that-be quietly lay the real groundwork for dictatorship. Once that groundwork is fully cemented, it will not matter who the autocrat is in charge, he will be a figurehead.