I don't remember people thinking HW Bush was dumb. Or McCain, or Romney, or Ryan, or McConnell, or even someone like Gingrich. Quayle, Palin, W Bush (very incorrectly, dude was wrong and/or lying about a lot of stuff but he wasn't dumb), and Trump, sure.
The thing those people have in common is that they have unorthodox public speaking styles. Especially Trump. It's kind of a pro wrestling adjacent style -- lots of performative bombast, specific tropes referencing cultural touchstones, I'm not trying to change anyone's mind on any substantive issue. I'm just trying to put myself into a particular box in the viewer's mind. It can be effective, but when it's not, it comes off as buffoonish.
The thing those people have in common is that they have unorthodox public speaking styles. Especially Trump. It's kind of a pro wrestling adjacent style -- lots of performative bombast, specific tropes referencing cultural touchstones, I'm not trying to change anyone's mind on any substantive issue. I'm just trying to put myself into a particular box in the viewer's mind. It can be effective, but when it's not, it comes off as buffoonish.