This ignores everyone else's agency in this decision.
The top employee is probably getting noticed and headhunted by the clients.
The top employee is probably getting pissed off at the mediocrity surrounding them, and annoyed at constantly having to share credit for their hard work with their bad manager who did nothing.
The top employee quickly realises that this is a badly-paid gig, and plans to spend the minimum time doing it that will confer the necessary Resume points.
The worst employee has no other options, is scared of losing this gig because they struggle to find other gigs, enjoys being able to hide their mediocrity in the team, and will stay as long as possible. They'll probably end up being promoted.
The top employee is probably getting noticed and headhunted by the clients.
The top employee is probably getting pissed off at the mediocrity surrounding them, and annoyed at constantly having to share credit for their hard work with their bad manager who did nothing.
The top employee quickly realises that this is a badly-paid gig, and plans to spend the minimum time doing it that will confer the necessary Resume points.
The worst employee has no other options, is scared of losing this gig because they struggle to find other gigs, enjoys being able to hide their mediocrity in the team, and will stay as long as possible. They'll probably end up being promoted.