In a possibly more pedestrian example, my organization needed a re-mailer service set up and found out that the IT worker previously tasked with administration for that service had the MFA set up for his personal phone. I think they eventually got a hold of him to coordinate transfer of credentials, but knowing him, there was a 50% chance he could have left the company on bad terms and would have made things quite a bit more difficult.
I had something similar happen when I left a company, only I'm fairly consistent on deleting credentials to systems I'm not supposed to have access to. Fortunately it was for an internal service and nothing customer facing, so they were able to wipe and redeploy.
One of the first things I do when leaving a company is remove all credentials from my password manager. Sure they should disable my accounts, but on the off chance they don't I still want it clear I don't have access.
It doesn't have to be a departure on bad terms, if they needed my TOTP codes I can't help them. That secret is already gone.
