> They aren't as powerful as you think
It's pretty common for C-level executives, and CEO's in particular, to be pretty chummy with the board of directors. They're all in the same social circles.
Often the CEO of company A will be on the board of company B, and and the CEO of company B is on the board of company A, so there may even be a quid-pro-quo element.
While the CEO officially answers to the BoD, in reality there's a lot of "understandings" and "gentleman's agreements" going on. This is why under-performing CEOs seem to stick around so long.