How do you even find a good GM?

Coaches have past records and stuff. That’s pretty reliable, good coaches tend to build winning culture and make the most out of players. But what about GMs? Most GMs fired from other teams are fired for a reason. Some are nepos. One or two years is largely due to luck sometimes, it usually takes 5-10 years to fully evaluate a GM’s choices if not more. So how do we know if Caserio is or isn’t the right one? Who’s even out there to target that wants to leave their good team? I just feel like firing GMs should only be done if the GM has shown continued incompetence, and despite my consternation about the OL the Texans have hit on enough picks recently for me to doubt we’ll find a better replacement. Yes the Eagles obviously draft better, but they are the best in the league and their GM is not leaving soon.