the reason not many spring to mind is because lots of successful teams don't change their staff that often including their manager, and 95% per cent of most managers (a blind guess) are appointed because of a few months success at another club and nearly all fail. Wenger started as a coach, Guardiola promoted from coach, if you are looking at success beyond that then you are looking at clubs doing well at a lower level with little cash and assistants regularly get promoted and do well
Obviously most start as coaches mate but to take over at a club you are working at is a different proposition , look at the bloke considered the power behind the throne at everton when Kendall was here . Colin should have cruised the managers job but he didnt because its different.
You not playing who do you complain to ? The assistant he can be your friend and tell you the manager should okay you but "we'll show him, get you head down cone of the bench and show him hey ?" . Well you can't do that at manager , you can't really have a drink and a chat with the players or tell stories .
What I mean is it's a totally different dynamic.