Almost everything will have cycles in IT. People want and security requires some kind of SSO. Now SSO is a dependency for almost everything, including the administration of underlying systems that run SSO. Same for the network. Same for a lot of things.
Bootstrapping from zero will never be easy and will always take some time. I don't think you can prepare your way out of this, short of preparing a fully redundant, fully separate secondary infrastructure.
This is called "break-glass procedure" in enterprise IT (as in "break glass in case of emergency"), and often consists of independent, normally unused, admin accounts on key systems, access info for which is locked in some safe location, e.g. physical safe in a secure location.
Testing this reliably is difficult, though, and often these procedures and their documentation is outdated.
I agree that fully redundant & separate infrastructure is unrealistic. I'm also not saying you can be 100% prepared. My point is that you can improve your posture.
What you can do is to have a sandbox environment where you periodically do a full setup exercise from a prepper disk. Conceptually it's not that different from testing backup recovery (ok, most companies neglect this too, so maybe you have a point :) ).
Problem is, the value of proper recovery procedures and testing those in all aspects only becomes apparent to the bean-counters when things really break. But until they have been in that situation where nothing works for a month, it will always be too expensive, too cumbersome and too resource-hungry to do those preparations.
Bootstrapping from zero will never be easy and will always take some time. I don't think you can prepare your way out of this, short of preparing a fully redundant, fully separate secondary infrastructure.