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.
Chelsea I would say were struck by karma after the unfair treatments to Thomas Tuchel early into the season, I still believe he wasn't given a fair chance to control the situation and try to make things right. They were lucky enough to escape been relegated at a crucial period and finish in 12th position. I hope Pochettino gets it right this time with Chelsea.