You can’t be stupid and work for Goldman Sachs, or get Seinfeld money.
Sure you can. Depends on the type of stupidity one is talking about. It is entirely possible to be knowledgeable (i.e, smart) in a given topic while being dumb as dirt in others. So you might infer that Bannon is financially smart due to his work at GS, but he is extremely dumb to betray the President of the United States the way he has done.