I think there is another reason why Napoli's president fired Spalletti after he won the Italy Serie A title for Napoli; it was not Spalletti's fault that Napoli was knocked out of the UEFA Champions League competition. Napoli was knocked out because Osimhen was not 100% fit to play for his club when he was needed most, and Napoli was knocked out. I believe Conte will not allow Osimhen to leave Napoli for any other club because he knows what he can achieve at Napoli if Osimhen remains at Napoli. Conte will need to strengthen his mild field and defense so that he can use his favorite formation without finding it hard to win matches when the Serie A league season starts.
I agree with you, there's is some reason why Napoli's president fired Spalleti after winning the Seria A title for the club, I don't think they will sack him for no reason after helping the team to lift the trophy they have been fighting to win for many years. The Napoli president always sacked coach who cannot perform well for the club because they always want positive outcomes in their games, and I believe Spalleti is among the best coach they have been appointed. For many years we haven't seen Napoli dominating the league as they did under Spalleti. But we have seen how strangely Napoli performed this season, they sacked many coaches which had an impact on their games this season. I hope Conte builds the club to the top next season.
Osimehn on the other hand, I'm not sure if he is going to stay at the club next season, even though they will be under a best coach who previously managed some top clubs in Seria A. Osimehn needs a big club to shine, he needs a big clubs who can participate in the next Champions League. Though, Osimehn was unable to score many goals this season because of injuries. Did you think Conte will not allow Osimehn to leave the club, what if Conte decides not to use Osimehn as their top striker? Osimehn has already done his best for the club after winning the league title. If he stays at the club for more years it may affect his football career.
The sign is written on the wall that Osimehn will not be Conte's favorite striker at Napoli because Conte already has eyes on signing Lukaka, which will make Osimehn to have less playing time at Napoli. I know Osimehn helped Napoli to win the Serie A title. After so many years, they have tried to win it, but they failed. Osimehn's good times at Napoli are coming to an end. He should leave Napoli and join another big club to save his football career. If Osimehn remains at Napoli and Conte doesn't give him playing time, it will be difficult for him to sign for another big club because they will believe he has nothing to offer again.