His accounts would have been shut down the moment he was fired, that is always the case everywhere. There was no chaos when he was fired. There was chaos after he was fired.
I've noticed something about reality. You know what makes sense in reality. You know the procedures, the logic, the rules. You expect the world to evolve according to them. But it rarely does. Case in point this entire episode of firing and rehiring Altman in the span of less than a week.
There are those things that happen in life, if a writer puts it in a screenplay, you'd think "what a bad writer". And yet...
Even if they didn't revoke his access, he'd be smart enough not to access their systems and leave audit logs, thus leaving a window open to be sued/prosecuted for exfiltrating trade secrets and proprietary IP (even if he didn't do so). That being said, knowing where the bodies are buried and having insider knowledge of IP are powerful motivators for retention
You can literally wake up your laptop from sleep and it restores the connection by logging you into the last session with the same auth. Not that easy to get sued for something as basic as that.
There are those things that happen in life, if a writer puts it in a screenplay, you'd think "what a bad writer". And yet...