It is quite reasonable if a company's response plan for scenario "what if we intentionally shoot ourselves in the head" is "don't do that, why would we do that?".

Abrupt firings of everyone with critical access, primaries and backups, is not, because its suicide. (Also why critical access roles are vetted carefully, because you want to make sure there is a lower-than-normal chance you will need to fire any of them, since that’s how you minimize the chance of a situation where you’d want to fire enough of them to cause a critical situation.)

If you do need decide there’s a problem that requires you to fire those people, you find every way possible to delay firing some of them while you expand the set of people with that access (which may be only momentary, by compelling them to hand over credentials as part of the exit process, if you have confidence that you can do that successfully.)