I think he's a lot smarter, or perhaps shrewder, than most people, especially the media think (or he's got great advisors). He's going to be attacked and ridiculed anyway, at least he's (for the most part) controlling the subject matter.
I could be wrong. Maybe he's a dumbask who's just getting really lucky. I think it's more likely he's gotten to where he is by stealth. We may never know, but that's my opinion, for what it's not worth.
In the 40 years that Donald Trump has been a worldwide name, and among the thousands of people Trump has interacted with in his many roles and long career as a builder, I doubt any have said that about Trump. More likely they thought, watch out for this guy he’s smart and he’s shrewd, as you first suggested.
Of course after getting into politics came the inevitable mudslinging and his transformation into Hitler, Stalin and Darth Vader combined. And, in addition to being an evil genius, from listening to his critics, you’d think that Trump is dumb and stumbled into his billion dollar empire. You know, the guy doesn’t even read, much less know what’s in the constitution...right? Funny, but in all the years before politics, no one ever accused Trump of being a racist.
But Trump knows how to build a wall – as well as what’s in the constitution. His company built a million walls. And I think millions of non political people as well as his political base see exactly where Trump stands on issues important to them and wholeheartedly support his agenda and what he says in his tweets.