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.