Saudi Pro League has lot of money which gives them advantage in signing players. If they join competition European teams will have hard time getting players they want. Antonio Conte wants Lukaku but Chelsea won't sell him cheaply or easily. If Napoli lets Osimhen go it means they want to rebuild their team with Conte. After bad season with three different managers Napoli can become strong team again next season. With Conte in charge and focusing on Italian games Napoli can compete with best teams in Serie A again. It won't be easy for Conte but he has the skills to help Napoli improve.
Conte's desire to bring in Lukaku could indeed be a wrong option because Lukaku still has the instinct to score goals. But Conte also has to look at the options of several other players whether it would be very suitable if Lukaku were brought to Napoli because Osimhen himself is still not certain about moving from Napoli to another team. Although most people probably believe that Conte can bring Napoli back to compete with the other top teams in Serie A next season.
When Conte said that he wanted my injury, then surely he had carefully considered what he would do with Napoli next season. It's impossible for a coach to say something without him having a plan with what he says, so I'm sure he has a plan with Lukaku. It's still not certain that Osimhen will leave Napoli, but it's still not certain that they can bring Lukaku, so this is still a question mark.
The scenario is that when they succeed in signing Lukaku then maybe they will sell Osimhen, and if they can't bring in Lukaku then they might keep Osimhen. Or maybe they will make a player exchange if they reach a mutually beneficial agreement with each other. There is still quite a lot of time left and in that time something could happen that they are planning.
There are big hopes coming from Napoli after they brought in Conte, hopefully Conte can perform according to expectations.