Nagelsmann was working at Bayern Munich and they got him fired from the team because of the bad relationship he had in the team with some players including Manuel Neuer and the bad performance he had, that's why Tuchel got his place in Bayern Munich got he couldn't have a good performance and failed to get the results they wanted to see which made Bayern Munich in the situation to even be close to losing the Bundesliga title after years of the winning this trophy, that's why Bayern Munich is thinking about another coach to take the place of Tuchel in the team.
Now their former coach Nagelsmann is working for the German national team, They asked him if he would return to Bayern Munich and start working there again, however, Nagelsmann didn't reject anything but he said everything possible.
https://dailysports.net/news/everything-is-possible-bayern-munich-ceo-on-the-possible-return-of-his-former-coach/I think Nagelsmann success at Bayern Munich at that time still seemed to be related about Lewandowski great performance. But yes, after Lewandowski left, Nagelsmann was also unable to produce good results at Bayern Mnunich. Also, in reality, when Nagelsmann was fired, it was at that moment that Nagelsmann also had a big chance of failing to bring Bayern Munich to get the Bundesliga trophy. But it is unfortunate for Tuchel this season, because it is still difficult to restore Bayern Munich performance, but at the same time the Bundesliga was shocked by the great success of Xabi Alonso at Bayer Leverkusen. With factors like that, I personally cannot blame Tuchel for Bayern Munich's failure this season and also, I cannot say that Nagelsmann is better than Tuchel because the moments that occurred in their eras were different.