I think Thomas Tuchel was sacked because at some point he wasn't getting wind for the Chelsea team which his boss wasn't comfortable with and having in mind of replacing him with a better coach everything became worse for the Chelsea team. I believe Tochel wasn't sacked because of emotion rather he was sacked because much was expected of him which he couldn't deliver and after all, none of the coaches brought back the lost glory to the Chelsea team
Tuchel had bad relationship with Chelsea director and owner during the last summer. He disagreed with transfers in the club and it continued after the season start. Some bad results during such bad time are enough for Chelsea owner to take advantage of it to sack Tuchel. It could be a decision which comes from individual conflict rather than for the club benefit. After Tuchel, Chelsea made two bad choices with Potter and Lampard and they consequently had very bad results even spending hundreds of $M in this season.
Under new ownership we have three coaches which bring Chelsea from band to worst which is surely surprising with this all mostly are blaming new owners for this all as their interference creating problems which is never been ideal for any team but now as they are doing things with Pochettino is also agreed with all terms and conditions hopefully we will have better results from them because no doubt he has done good job at Tottenham which is never been ideal club for any top coach due to limited sources.
Sacking Thomas Tuchel was surely bad decision from new management, but this all happens due to bad relationship between coach and new management, so now wait for the next season and performance of new coach and team which is going to overhaul in next few weeks.