Earlier quoted context omitted.
This is how it works in normal software companies too. I never see the credentials for my employees.
My point is, as a manager one can request that their subordinates get credentials to access systems. Therefore as a manager you could create a fictitious person (or use one that's recently left the company), and have them be given credentials to access those systems. Then you could use that fictional identity to do whatever nefarious things you want to do. Then again it could be just as simple to create an alternate…
The former restriction is maybe difficult enough to efficiently implement in an organization that it's excusable (we have a scheme for it at $work, but it unfortunately means that sometimes people show up at work and the paperwork isn't ready yet and some of the accounts they need aren't yet ready).
The latter, on the other hand, is security 101 and not implementing it on the production floor is just irresponsible. I really hope it's not what happened.