Things are turning worse as same as in the past season when Frank Lampard lost his control after winter and Chelsea gradually fell on the table. Eventually, Frankie was fired and Tuchel came to make a history. A history of Chelsea is interesting but risk for Tuchel. It's rarely to see a coach can save his position after winning a title in a previous season.
In my opinion, the main reason of Frank Lamapard's failure was that in order to discipline some members of the squad , he didn't used those players who didn't followed his directions properly. Take Rudiger and Alonso for example, under Tuchel they are the backbone of the defense. There should be some degree of discipline but not too much. Chelsea right now seems to have lost a bit of focus but once they gather that back I think they will be back in form.
There's no much difference between Frankie and Ole, they have a clear understanding of the clubs system but not the right Manager for them.
Aside that, no English manager has ever won the premier league, so no doubts I knew there was no way for him to do better than he did, since he was tipped to win the premier league.
Thanks to Thomas Tuchel, they did improve greatly.