It is important to recognize that CEOs are members of an exclusive club. Yes, someone like Zuckerberg can start his own company but at some point the investors bring in the "pros" to be the CEO, CFO, and COO. You might think by "pro" we mean someone who is real good at their job and in a sense they are, the problem is their concept of their job and your concept are two very different things.
I used to be a stock broker and I would see a CEO drive one company into the ground, into bankruptcy and then immediately get hired to be the CEO of another company. That particular CEO is an expert at bankrupting companies. Why would you hire him? Because I can make money on a stock if it goes up or down, just so long as I know ahead of time what it is going to do. But wait, the CEO and board of directors cannot sell their stock without triggering all kinds of legal issues. Exactly, this is why I say it is a club. If I have a portfolio of 25 stocks, I can take a loss on one stock as long as I make out like a bandit on the other 24. Because this guy bankrupts the company and lets all his friends know, they in turn help him out. How do I know? They all sit on the boards of each others company and you can do no wrong, your company goes bankrupt and then you are hired immediately somewhere else.
So when you are talking about the Fortune 500 companies it is a very tight club and the amazing thing is how many of these very busy professionals are members of FreeMasons, a secret club that requires you to promote anyone else in the club that you can promote or in some way benefit their business. If they are bidding on a contract you give them the inside baseball on how to win that contract, etc. This is why the percent of CEO's that are sociopaths or Satanists are about 25x that of the general population.