The sudden change of coaches with the intention of wanting to improve the club actually backfired for them and can be said to be the biggest mistake. Even though Nagelsmann also can't say they can be champions when not substituted but still in this case he has more chemistry than Tuchel.
Tuchel isn't bad as a coach, it's just that he needs a bit more adjustment and as the game drew to a close he came on it was clear it was a tough road to overcome.