Yes, I believe Tuchel was hastily removed as he would have been given more time to make things better in his own way.
Tuchel was removed because he was a remnant from the past owner of Chelsea. The new owner needed someone who he could believe in as the right choice, but clearly he has made a mistake with Graham Potter. Bad thing is that Chelsea gave him a five year contract and to let him go now will mean them paying him off hugely since they are the ones breaching the contract. They have spent a lot this season and know that letting Graham Potter go will cost them more money, so perhaps the best choice for the business is to give him some more time maybe till next season.
Now we all can say that it is a mistake made by Chelsea's owner in choosing Potter, but we all also forget that it is not easy to manage a team for a coach who come in the middle of a season.
I would prefer to say that the mistake is the decision to change the coach when the season is running a half, I do even doubt that a better or more experienced coach will be able to do better than Potter for this situation.
Of course the best thing is to give him at least a whole season to prove that he is a capable coach who can bring a better achievement.
I think Potter will need to rebuild the team first in the next new season if he wont be sacked at the end of this season.
I don't agree with your assessment. Chelsea's major setback was clearly at Potter's hands. I think he has had enough time to manage Chelsea, he is also a local English coach, so it doesn't take long to adapt. Potter has also been involved in the big transfers that Chelsea have made, a number of potential young players at a high price he has signed. Then besides that, the legacy player from Thuccel is a great player who is experienced enough. I don't think Potter is fit to manage a team as big as Chelsea, he isn't experienced enough and he isn't ready for big pressure either. I think Chelsea's management must have the courage to take decisive action even though it has to bear huge costs, the partnership with Potter must end immediately.