I heard an interesting version that one of the reasons Tuchel was fired was that he divorced his wife and started a relationship with a girl who is much younger than him. Thus, he lost the respect of the team and the confidence of the players that Tuchel focused on football. Naturally, this was not the only reason, there is always a complex of different reasons, but at a certain moment this also played a role and shifted the scales towards dismissal.
I'm not sure if this story is true because if Tuchel actually did something like this it will be serious issue that will be heard in all corners but this stories sounds like a rumor, if this led to the sack of tuchel I don't think chelsea won't let it know to the public and fans. The reason tuchel was sacked is because chelsea was not performing very well.