I think the Bayern board fecked this up badly. Tuchel like any new manager needs time and his players to build his team. Changing the manager so late in the season just unsettled the whole team.
Some players seem to had issues with Nagelsmann, but others like Kimmich had a great relationship with him.
If they wanted Tuchel that badly they should have agreed on a move in the summer and let Nagelsmann finish the season. Now they threw every competition out of the window and the new manager starts his first full season on a downer, genius move really.