So, the "President"'s doctor says Trump's cognitive ability is fine and there's no reason to believe he's suffering any kind of decline or dementia.
I have no trouble believing that.
As much as it might be in some weird way comforting to think that President VonClownstick is a demented old man and that's why he says and does the horrible things he says and does, there's no reason to think so. It'd be one thing if there had been an observed change in his behavior, but aside from Michael Wolff's observation in the Fire and Fury book that he's taken to repeating himself more often than he had been previously, I don't know of any. He's been this same sort of racist blowhard misogynist ignoramus moron the whole time he's been a public figure. Presumably before that, too.
He's completely compos mentis. He may be (and is) a narcissistic, vain, incredibly insecure egomaniac; he might be (and is) a bigoted, mean, willfully ignorant sociopath; he may be (and is) a weak-willed, greedy, and fundamentally cruel fool whose lack of intellect and dearth of knowledge makes him an easily-manipulated danger to all of humanity; but he's perfectly sane.
What I do have some trouble believing is that the man weighs only 236 pounds. That rings about as true as the back of Terry Forster's baseball card.