One piece of data is that there's an inverse correlation between CEO pay and company performance:
https://cooleypubco.com/2016/07/25/new-study-shows-inverse-c...
(1) Long periods of success lead to raises for the incumbent CEO and then the long period of success ends
(2) The company is failing and needs a turnaround. No external person is willing to take the job for normal CEO pay for the company’s size because they know they’ll likely fail and that makes getting another CEO job substantially harder.