It's not always the case with the manager. I'm friends with a recently retired ex pro who had a pretty solid career, he mentioned in the past he moved clubs simply because he wanted to live in a certain area, or that the move would put him in the shop window more than the current club he played for. I think the influence of the manager is less so than it was 10, 20 or 30 years ago, especially as most barely last a couple of seasons.