I think that some of Trump's aides, like Kelly and Conway, are smart and competent people (their ethics, actions, and beliefs are a different matter, of course). But he's also surrounded himself with plenty of incompetent boobs as well, including his sons and son-in-law. The problem is that Trump often doesn't listen to his own "powers that be" - he clearly sees himself as smarter than everyone else and often listens to nothing but his own impulses and instincts. He probably isn't even smart enough to be aware that he can't fire Mueller by himself - I could easily see him trying to fire Mueller via a tweet without consulting with anybody. He has almost no understanding of how our government works - it's clear he really did see the federal gov't as being like his business, where he gives orders and everyone else is supposed to follow them. Maybe he'll listen to people about Mueller and keep his mouth (and twitter account) silent, but he hasn't done so with virtually anything else thus far. The longer this investigation goes and the more people Mueller investigates and charges, the more frustrated Trump will become, and it wouldn't be a surprise if he just finally blows his top and does something stupid. Trump's advisers may not be dumb and impulsive, but he certainly can be.