I don't agree with you.
Nagelsmann's problem was not just a problem with results and team performance. Nagelsmann had a bad relationship with most of the players which had a negative effect on the team.
Correct, it would have happened even if they were performing alright. There was lot going around prior to his sacking like leaking of his strategies and all so there was lot going on behind the scenes which we still don't know yet. This season was a hard pill to swallow for them, but they have to accept the fact now.
Tuchel will have proper time next season to know his squad and assess his options according to conditions, so I expect a better consistent form from Bayern next season. Tuchel has Bundesliga experience with side like Dortmund but like every manager he also needs time.