The fact is that Tuchel career as Chelsea coach was not so bad, during his leadership era, Tuchel managed to bring Chelsea to win the Champions League, European Super Cup and Club World Cup titles. But all the achievements that have been presented by Tuchel are no longer visible due to a series of poor results obtained by Chelsea at the beginning of this season. The last defeat that Chelsea got from Dinamo Zagreb made Chelsea Management take the attitude to break the cooperation relationship between the two, Tuchel became the first coach to be sacked in the era of Chelsea new ownership (Todd Boehly).
Graham Potter presence in the coach seat is expected to make Chelsea a feared team again in the Premier League. Potter has a good record during his time as Brighton coach, Graham Potter cold hands managed to bring Brighton to look good at the start of this season. Potter genius in strategizing managed to bring Brighton to fourth place in the standings list. Due to a series of good results that Brighton got, Todd Boehly immediately applied for a 5 year contract for Potter.
Chelsea's defeat to Dinamo Zagreb was just the final stroke that had to break Tuchel's relationship with Chelsea but there was a problem with Todd over transfers most notably the issue of Ronaldo. Todd wanted to sign Ronaldo but Tuchel didn't want him, so there was issues before Dinamo's defeat
As for Graham Potter, fingers crossed, let's wait and see. We all know how coaches like this turn out in big clubs. Example is former wolves and Tottenham coach Nuno Espirito, how he faired in wolves and after moving to Tottenham the move wasn't a great one.