There is a big difference between smarts, information and the ability to think quickly on one’s feet.
Politicians are usually so glib and rehearsed that people think they are a lot smarter than they are. Most of them are just high level used car salesmen. No insult to salesmen intended.
Obama’s a perfect example of that - when he’s on prompter, he does sound intelligent (unless you actually examine the substance of what he says).
Off prompter? A bumbling fool.