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.
What if the team loses more before next season than if they recorded a loss and took Potter out? For example, if they don't make it further up the grid in the champions league? Right now the team is in 10th place in the league and most likely may not even qualify for the Europa League, which would probably be the first such case for Chelsea since Abramovich bought it.
That's not counting the money the team won't get from European cups and broadcasting royalties.
All in all, given the overall situation and the losses Chelsea may suffer, a forfeit to Potter seems like the lesser of evils.