It seems that Bayern Munich's decision to sacked Julian Nagelsmann seemed very hasty without technical considerations, he managed to achieve positive results in the Champions League with 8 wins from 8 matches and an extraordinary achievement for the Bayern Munich team, especially against big teams like Barcelona, Inter and PSG at 16th round.
However, on the other hand, Bayern Munich's management was not very happy with Bayern's achievements in the Bundesliga after being 1 point left behind Dortmund on current standings. Maybe this was strong reason for sacking of Julian Nagelsmann, which shocked the public because of his extraordinary achievements in the Champions League.
I agree with you, they should be able to wait until the end of the season to evaluate Julian Nagelsmann's performance because so far Bayern Munich are still on a good track to win the treble this season. And finally they officially announced the signing of Thomas Tuchel, I don't know what the directors of Bayern Munich are thinking at the moment. It could be, this decision will be a suicide bomb for them, we'll see what Tuchel can do for Bayern Munich in the remaining matches this season.
Changing coach in the middle of competitions usually will have bad impact for the team performance and besides you most people also complaining why Bayern management suddently sacked Nagelsmann without any spesific reasons and Bundesliga still have 9 matches remaining which is every matches could be crucial matches for Bayern because if they lose one or twice in the remaining matches i am sure Bayern will lost their title this season
And i personally doubt Tuchel will bringing positive impact for Bayern performance considering he was given very tight time to build a team but we will see the indicator of Bayern performance under Tuchel next weekend against Dortmund that if he can successfully to win from Dortmund probably he will bring Bayern to perform better than under Nagelsmann