Actually the longer contract runs, the smaller transfer fee Napoli can ask for. That's why usually if a player wants to move to other team, he will wait until he has at least 1-2 years remaining in his contract, so his transfer fee would be cheaper. Napoli might hard to reject big amount of money but for Osimhen himself, a big transfer money will get him burdened, especially if he decides to move to Premier League, where media always keeping an eye on big transfer players. Both of Napoli and Osimhen sides having a great time this season and it would be a waste if they decide to separate next season.
No, you are wrong. If you have a player under contract for five years and another club wants him really badly, the club has to pay for it a lot of money. If the contract expires in one year, the club really wanting that player offers you a smaller fee or just waits for the contract to expire.
The one who really benefits from a contract that is about to expire is the player himself because he can ask for a massive signing fee. A club who has a long contract with a player can have all the patience in the world unless another club comes and puts a huge bag of money on the table. That's different when the contract is just one year because the club owning the player can decide to either let him go for zero next year or get some money this year.
Not sure why you think that the transfer fee is smaller when a contract is longer...
I get your point, but that's wrong at all. Not sure where did you get that theory. First of all, let's separate the remaining contract duration and the desire of the wanting club on the player as the key aspects on football transfer. As I believe that we are discussing the second one, then we can ignore the desire of the interested team. So, imagine if in your team, there is one player who has 1 remaining season left in his contract. It means that in the next season, he can leave the club for free. Then, instead of getting 0$ in the next year from this player, you could get some good amount of money by selling him with fair fee. Because of what? Yeah if you keep putting high cost on this player, the interested teams will just wait until the player contract expired in next season. Why you risk of not getting any pennies by putting high price on a player whose contract about to expire next year?
Let me give you an example. Shinji Kagawa, brought by Man Utd from Dortmund with a bargain fee, afaik it was under $20M, while his value was higher at that time. But since his contract about to expire, Dortmund had no other choice except getting fair money by letting Kagawa go. That's also happened because Fergie didn't want him that bad. That means it's okay at all if Man Utd failed to sign Kagawa, so the situation favored Man Utd.
And now, finally the aspect that support your opinion, the desire of the interested team on a player. The fact is, that team dont care about how many year left on the player contract, as long as they can bring him, especially when they have strong financial support. But if we talk about the remaining contract duration alone, no, the less remaining contract duration, the lower transfer fee. You can read this journal paper for reference;
Econometric Approach to Assessing the Transfer Fees and Values of Professional Football Players. It's not related directly to our main discussion but there are interesting points mentioned there about transfer fee.