Currently, Napoli is still looking for a team that wants to buy Osimhen and Napoli are even willing to reduce Osimhen current selling price to 100 million euros from the previous 130 million euros, although Osimhen has been an important player for Napoli in the last few seasons but Conte doesn't want to keep him in the squad at this time and actually asked Napoli to bring Lukaku from Chelsea as their main striker next season, the sale of Osimhen will of course provide huge profits for Napoli and that the money can be used to strengthen Napoli in next season.
I don't understand why Conte chose to sell Osimhen and asked the club board to bring in Lukaku. Several reports stated that the sale of Osimhen was due to a club agreement and Conte could only agree to it. But apart from these rumors, I think Conte's decision to bring in Lukaku was because Conte had worked with Lukaku and Conte saw that Lukaku was the striker they needed right now. Another reason is probably because Lukaku can be obtained quite easily after Enzo Maresca did not include Lukaku in his game plan for next season so there is a possibility that Lukaku will still be sold.