Chads and Stacies are pretty much never actually smart (they basically can't be, since there's never been any evolutionary pressure for them to be).
It just seems that way because they get literally everything--including good grades, promotions, etc.--handed to them on a silver platter.
It severely fucks with incels' minds though because looks create the illusion of talent in every area of life, including things that require some minimal level of real intelligence (such as college).