Icahn says this. Basically the CEO is a survivor. He will never hire someone that is smarter then him. As time goes by the people slowly get promoted and so on and so on. These guys never making waves or going against the flow. He likens them to your fraternity president. A likeable guy, everyone knows him and he's understanding and easy to get along with. And he's a survivor he has always won and these frat presidents and what not have to get elected so he knows whats up.
So as time goes, the CEO keeps him along, and then when the CEO retires he puts in the guy right below him who is a bit dumber then him as CEO. To survive and make it in the corporate beuracracy you never want to hire people smarter then you, God forbid your boss sees your subordinates and fires you and gives him your job.. I've been in the corporate beuracy and I'm the same way becuase you CAN NOT make waves. If you do you get booted out. Nobody wants change, the structure is there and the companies are already generating tremendous amount of cash flow (100's of millions a quarter). To become CEO, just keep it chill, relaxed and don't make waves.
Btw, I've fired quite a few ENTJs. They want to disrupt the status quo so we fire them. Take that shit to a startup. And they scare most people. Esp the ones with a strong E. All in your face and it upsets people's regular chi energy. I remember actually telling someone "you wanna be a hero, you can't do that here. Go to a startup".