I also think the same as you, Conte's decision to sell Osimhen, is very unfortunate, whereas if you think about it, if Conte had paired Osimhen with Lukaku, Napoli would most likely have great ammunition for the front sector, even becoming a big threat to Serie A clubs and Napoli will be a club to watch out for in Serie A this season, but the decision that Conte has taken is a unanimous decision and it cannot be denied that he knows better about Napoli's future development.
Conte does not want any gaps in his squad, the decision to cross Osimhen out of his squad was due to the conflict between the player and the Club. It must be admitted that Osimhen is a talented young talent and in my opinion Conte also really needs Osimhen in his squad, but as a coach he must take a stand for the good of all parties so that no one is harmed.
Conte is not too worried about Osimhen departure because he can still rely on Khvicha Kvaratskhelia to accompany Lukaku in the front line. Kvaratskhelia will be Conte's mainstay in the front line because he has contributed 26 goals and 27 assists from his 92 appearances, even though Napoli is currently without Osimhen, but the presence of these two players in the front line will make Conte calmer in handling Napoli.
Conte has done his best, it is impossible for Conte to maintain Osimhen with all the conflicts or feuds that exist, it actually makes the Napoli team unable to rise, regardless of Osimhen's very good quality, but if he does not have a harmonious relationship with Napoli management or with other players, then everything will be in vain. And for Osimhen's replacement, Napoli has now found it, they have brought in Lukaku and that is Conte's wish so I think for the whole Napoli team there are no problems now, especially for their front line and losing Osimhen does not have much of an impact.