The rationale behind these salaries is that these highly compensated CEOs make their salaries and more for their companies.
This may or may not be true. I'm inclined to believe that it isn't. I'm inclined to believe that many other candidates could perform comparably or perhaps even better. But maybe not. Maybe in our society people are too obsessed about having more than their neighbor, too obsessed with Real Housewives, and not obsessed enough with being their own person with dignity to the point that having these CEOs who lack any sort of humility and who frequently tout their value and uniqueness is the optimal choice to run many of our companies.
Fun fact, the CEO/founder of Zappos makes less than $50k (granted, his company is worth a little under a billion). He lives in a trailer park which he has made into a sort of tech community.