I had severe anxiety issues I hadn't had my entire life, or actually not since the last time I had a terrible boss. They got promoted out, and magically my anxiety went away. I had not made the connection until after they left. I thought they weren't a great manager, but I didn't realize how bad they were until I was no longer under them. I felt directionless under them, they would ask me to spend more time on a project to see if I could accomplish some unlikely goal (my job is very research focused), the criticize me later for taking too long. They regularly made jokes about firing people, etc. They hated their job (being a manager) and it showed. I thought it was kind of funny at first, thought it was part of their personality, but didn't realize it was actually having a severe background effect on my sense of accomplishment in the job.

I was on medication for all this, I think there were other factors, but it was a massive relief when they were gone. I am now on a new team and killing it, later I found out the manager trash talked me behind my back, other people left as a direct result of working with them/under them, and their attitude is carried into other environments and their new role, where its highly unprofessional.