No but your logic was, if the coach that comes in for another one is a top manager, a "real" manager and top class, it will get better and he will get results. Bayern shows that this is not always the case.
I can guarantee you that every manager coming in atm would struggle, bc these players have written off the league mentally already. They just wouldnt perform no matter who the manager is. In their minds, they have already finished the season and are just preparing and training for next one. Its literally training games for them.