I think one must distinguish between stupid and crazy. Let me illustrate...
A man blew a tire on a road beside a psychiatric hospital. As he was putting on the spare a wreckless driver clipped the hubcap in which he had placed all 5 wheel nuts flipping them into the adjacent ditch. After half an hour searching he only came up with one wheel nut. He was absolutely clueless until an inmate of the institution who had seen the whole thing through a window commented.. "Hey, why don't you remove the other hubcaps and take one nut from each wheel, put your spare on and head for the nearest garage?"
Incredulous, the man looked up and blurted out, "You are so smart, what are you doing in there?" The inmate looked down and confided, "Look, I may be crazy, but I'm not stupid".