From the loss of Robert Lewandowski to the team performance Bayern Munich started to dwindle their performance and it is likely shown at the start of the Bundesliga that Nagelsmann is always insisting for Sadio Mane be a top striker just like Lewandowski which is likely not happening because Sadio Mane wants his original position so Nagelsmann don't have any solution with that at the start of the season for Bundesliga but when he let Sadio Mane in his natural position Bayern Munich have performed well again, and even making incredible dominance wins,
The biggest mistake was not the selling of Lewandowski for Bayern Munich in fact. It was their not making any effort to fill his place in the same transfer window. I wonder whose call this was because it was nonsense. Lewandowski has been one of the players who made a big effect on Bayern Munich's dominance for years. His goal contribution was really insane. You just can't expect Choupo-Moting or Mane to show the same performance by playing in that position. It doesn't make sense considering these players.
Mane should have played on only his wing and Choupo-Moting should have stayed as a rotation player. Because of not making the needed signing they struggled even more in many matches this season.