it seems like you are forgetting something that the players are not at fault but the coach + owner of Napoli is.
now let's try to understand first that before Spalletti was fired, Osimhen and the other players could appear more consistent and have a very stable performance and be able to perform very perfectly in every match.
but all of that was destroyed after Spalletti was fired simply because he couldn't help Napoli get the UCL title and what's even more ridiculous is that in one season Napoli replaced the coach 3 times.
I don't want to blame any party but it really doesn't make sense if the players have to be stressed by changing coaches all the time and have to adapt quickly to every change of coach and of course the Napoli players will not be able to perform according to the new coach's strategy.
maybe that's the reason Osimhen has the desire to leave Napoli because of the selfishness of the Napoli owner which could create obstacles for a talented player like Osimhen to have a perfect career, so Osimhen wants to leave Napoli.
of course Chelsea will fail to get Osimhen for the right reasons, currently Chelsea is experiencing the same problems as Napoli even though they have many talented players but in terms of competing for the top of the standings it is always difficult and of course Osimhen chose another team which is more guaranteed to give Osimhen a future career. which is more perfect.
He will need consistent philosophy to be able attain his height.
this inconsistent performance has made him ready to leave the club and at this point, he has now received. Osimhen to Chelsea isn’t a bad move as the club will be able to help build him as a young player till he attains the height he wants to.
Now clubs should learn that they need stability to be able to help players build as without that the players might not be able to deliver on a stable and consistent performance and this will be really a bad one as the players tend to decline and most time want to sought better time and training including stability elsewhere.