Lukaku can even be said to be the most patient player which shows that he is very kind-hearted. He continued to be loaned out by Chelsea for several seasons but Lukaku was always able to immediately adapt to whatever team he was loaned to. So it is not surprising that Conte always likes this player. Because Conte knows everything about Lukaku in the past. So Conte already feels comfortable with this striker. Lukaku even immediately showed his quality at Napoli. So Conte must feel proud because he asked Napoli to bring in this player.
Lukaku is a strong man and a good player with high professionality and he's very skillfull too. He was loaned out to different clubs because he was treated badly in Chelsea and his relationship with Chelsea was entirely broken and won't be able to healed. In any club he joined as a loaned player, he played and lived entirely for them so by taking a player like him, many clubs can get good benefits while main part of his salary is paid by Chelsea. It means these clubs spent very little cost to Chelsea while they got a lot from Lukaku.
Osimhen he is still young. And yes, he was a little complacent with the achievements he got when he was able to bring Napoli to the Serie A title in the previous season. but last season he failed to show his good performance again. And then his relationship with the club deteriorated, which led to his desire to leave Napol. And to be honest, I want Osimhen to go to a big club that can maximize his potential. But unfortunately he failed to find a team willing to redeem him at a high price. And now he has to accept that he will be loaned to a Turkish club, namely Galatasaray.
Osimhen is younger than Lukaku and even he plays at the same striker position like Lukaku, he has different playing style. With different playing style and skillset, Osimhen can make many different contributions to his club compares to Lukaku. Losing Osimhen is a big loss in player resource for Napoli because recent seasons, he was an important player and piece in their tactical operation. Anyway, life spins and Napoli have to move one without Osimhen while the player has to develop his career at a new club.