I agree that Chelsea is having some sort of trouble that is beyond the manager. There is a feeling in the club that makes everyone upset with whatever they have and they lost hope that they could ever be good. They need a manager that is not just a tactician, that's not going to cut it because tactics is not the main reason why they lost. They need someone who can bring the best out of the players and make them feel hopeful about the future again.
It is common reason why when a club falls into a crisis when very bad results and conflicts between coach and player, club usually will choose their players and let their coach goes away. Especially in big clubs with many star players who have good quality but only need good system to play in and contribute their best with their best mood. When they have better mood with a new coach, their contribution will become bigger at least in short term with a new coach.
Osimhen injury isn't that bad and I think he will be ready to be back on the pitch when he takes on AC Milan in the UCL. but there is no definite certainty because anything can happen meaning that if the recovery goes well then he will return quickly to the team but if there are problems during the recovery period then I am sure he will be absent when facing AC Milan in the UCL.
I don't know it is good or not too bad but if he won't be able to play in a first quarter final match with AC Milan, it will be bad for Napoli. I can not verify the information from
Sportsgambler which says that Osimhem will be missing till mid April. It means Napoli are facing risk of losing Osimhem for that match with AC Milan.