Whatever one may think of his policies, it's an undeniable fact that he won re-election by a remarkable margin, so he must've done something right. And I don't think he's suddenly become so much worse since then. Though no doubt he has been focusing more on his presidential campaign than on his day job since then - Floridians might be happy that he had to drop out.
Sure, I buy that there's more to Trump than the persona he likes to display in public, on The Apprentice, or in politics. And he couldn't have had the career he's had without having a particular kind of intelligence and skills, obviously he's not like a three year old in that respect. I do not think he's too dumb to be president; I think he's too much of an egomaniac and too perfectly indifferent to everything other than his own ego to be president. It's less that he couldn't properly do the job than that he doesn't want to. A big ego comes with the territory for politicians or businessmen at that level, of course - but still there's gotta be a bit more than that.
I mentioned the late Silvio Berlusconi in another post - in many ways very similar to Trump, both in personality and in general career trajectory. I loathed Berlusconi almost as much as I do Trump and for the same reasons. Perhaps the differences that I do see aren't even really differences in personality, more forced by the particular circumstances of their respective countries - but either way, at least Berlusconi could and did cooperate productively with other politicians, inside Italy and outside it, when it was necessary. Trump is just a would-be dictator who doesn't even care enough about policy to have to worry about cooperating with anyone - though I guess from a certain perspective his lack of interest in policy makes him a less threatening kind of dictator.