1) An inflated view of the impact of execs compared to other employees. This is a well studied psychological phenomena. People tend to overestimate their "skill/contribution" even in poor luck or even rigged scenarios. (There was a study which gave some subjects a head start in monopoly, i.e. more money, the subjects tended to talk significantly more about the advantages of "their" strategy in the game, then the subjects that we not given the head start).
2) It's in the interest of execs to keep C-suite salaries high, because it increases their own salary.
So it's not surprising that we have seen a dramatic increase in ratio of exec to average employee compensation, and why execs are typically isolated from economic downturns.