And as if Tuchel will do any better. Mourinho, Grant, Sarri, and Conte have all mentioned how the manager there basically has no say on transfers, and usually even line-ups. I'm sure they called Allegri (probably Nagelsmann too) and he sees how they treat managers and how they run their club and probably told them to piss off.
Abramovich and his cronies are basically the Jerry Jones of European football.
I read an article in The Athletic about it. According to them, Chelsea had reached out to several big name managers and none wanted anything to do with a partial year job. Even Tuchel turned them down at first before reconsidering.
It's really a no-win situation for any manager there.