It’s amazing how much the industry leaders just copy each other. Google didn’t throw the towel in until Amazon did first.
For-hire CEOs often are also paid in equity, not just stock options. But even with just call options (Which have no downside risk), there is the risk of the professional reputation of the CEO, if you just do middling for a few years and leave, still plenty of job opportunitiess. If you crash and burn the company down... Very tough to find another good exec position again.
Is this really a surprise to anyone at this point?
They weren't axed. They are choosing to leave. They probably reached the point where all the incentives to stay were earned and have no other reason to stay. The Fitbit acquisition was completed 3 years ago so it is quite likely they have reached full vestment.