Sometimes it is, sometimes it isn't. If a manager has to fire a lot of people under them, and there is consistent feedback that it is a surprise, etc. that signals two things to that manager's bosses:

1. This person is having to fire a lot of people, something is up that needs to be investigated.

2. People are surprised, this person may not be the best manager.

The specific details are everything in this case, so it really depends. It can definitely come back and screw the manager though if it is indeed their own fault. Often times it may not be theirs alone though.