It’s clearly not about points on the table with Bayern. If they feel they can’t work with a coach, if the coach isn’t quite on the same page, or this current coach has no chance of winning the CL in the next 3 seasons, then the coach goes and the Bayern machine rumbles on.
They’ve successfully monopolised the BL and only lose it when they allow another team to win it. Their aim is to sign some of the best players in Europe and win the CL as often as possible. In the pursuit of doing that they will swap and change managers until they find a great coach with the right mindset. If you have a great setup like they do, and you don’t move on a coach that everyone feels isn’t quite up to it you just lower expectations and standards, then you end up like United and everything gets worse year on year.