That's from your own point of view. Osimhen has the final say. If United meets up to all the demands of Napoli and Osimhen did not complain, he will bein United. It's the moat seruous club amongst these three clubs that you mentioned, is where Osimhen will go. You cannot be suggesting he goes to a club that is not ready to get him. Chelsea had the opportunity to bring Mbappe over to Stamford Bridge but they downgraded his potentials. That alone will not make Osimhen think of going to Chelsea, because they wanted to take advantage of him when he has no club to play for.
It has been a long time since many clubs have wanted to bring in Osimhen, but they could not meet Napoli's demands and even if they dared to fulfill what Napoli wanted, they would not be able to negotiate with Osimhen, because he also wanted a high salary. This makes the process difficult and this can be overcome by clubs that are very intent and willing to spend more money on Osimhen. Until now I have not been able to see which club is serious and willing to spend a lot of money on this player.