Osimhen can be a very important player for Manchester United. Therefore, his transfer will be a great plus for the Red Devils. However, the real question is whether they will be able to make this transfer. Napoli wants a fixed fee for the transfer fee. Maybe they can offer them a Hojlund swap. If Napoli includes the young player in their plans, they can add Osimhen to their squad for free. I think Osimhen can be more useful in Manchester United.
Osimehn can be helpful to Manchester United, but the club is not willing to pay the player prices, perhaps they believe he is not worth signing in that way. Osimehn is interested in joining any Premier League team, but the club refuses to meet the price Napoli is asking for. If the player had not extended his contract with Napoli in 2023, he would have signed for a Premier League team, but he did so because of the league title they won, and many teams have yet to pay the fees Napoli is demanding.
Furthermore, I believe Manchester United prefers Gyökeres, a 27 year old who has a contract with Sporting Cp. Osimehn has rejected Al Hilal offer for the 4th time, the player is not ready to go to any Saudi club at this stage of his career, he wants to play in the Premier League, but Chelsea and Manchester United still do not believe the player is worth the amount that Napoli is requesting. Galatasaray is still interested in the player, but we'll see whether he can stay.
If no other club accepts the price put on Osimhen by Napoli, Osimhen will remain in Galatasaray because they're the only one that have shown much interest in him in Europe. I don't know why EPL clubs don't believe in Osimhen or they feel cheated on the price that Napoli is demanding which is one of the reason why both United and the rest cannot afford to sign him.