Usually C-level execs is all about connections or where they went to university. They are not smarter than folk in the trenches.
I worked at a company that was relatively successful because of the connections the CEO brought to the table.
Objectively, the company would have been far less stressful to work at - and more profitable - if we had a better leader, but it wouldn’t have existed without his connections.
I have, unfortunately, also seen something similar to your experience. This is why hiring for a role like that is tricky.
I want to say for the record I also once hired an awesome CEO who was humble, sincere, reasonable - and very effective. We're still friends after 25+ years.
At the core, C-level roles are often sales roles. They need to sell their ideas both up (to the CEO and board) and down (to their org).
You hire executives for different reasons. Sometimes loyalty or incompetence to a degree is valuable as the person isn’t a threat. Other times people are hired to drive a particular agenda and can be relied upon to do that because they are too dumb to do otherwise. And sometimes they are sacrificial lambs.
Unfortunately you can’t discover the strength of either until you’re in quite deep. That’s the risk.