Sociopathy and narcissism are overrepresented amongst executives. Smart people (as meant in the post) usually like to discover (scientists) or create (engineers, writers, etc.) things. They don't have to achieve power for power's sake in order to be happy.
Thus, they aren't as well represented amongst executives in established companies because that form of achievement isn't something they valued.
Not to mention that these people have the chutzpah to get what they want. They're always successful in the short term, which means that they've already gained influence by the time anyone figures it out. And when they do, that person gets canned as an example to keep the others in line.
Thus, they aren't as well represented amongst executives in established companies because that form of achievement isn't something they valued.