As far as I know, last season Osimhen had a very large transfer market value which made many clubs unable to get him. Napoli also won't let other clubs get it easily. Because of that, they set a high price clause for Osimhen. This season Napoli's performance has been very bad. Osimhen managed to score 15 goals and was among the top scorers but was unable to provide a good performance for Napoli.
A good player will not be able to provide good performance for the team if he can only work alone without any help from his own teammates on the team. So it would not be enough to say that Osimhen is a bad player because he does not get more good support from his teammates who may still be less able to provide the best passes to him when in the match. Because in fact he still has to be considered a good player at Napoli so that Napoli sets a high price for him so that other teams cannot reach him more easily.
When Napoli won the Scudetto even though Osimhen's transfer market value was very high, but other elite teams could certainly afford to buy him. But, because Osimhen chose to stay at Napoli, then the other elite teams failed to sign Osimhen. So, it's not about the high transfer market value, because Osimhen himself refused the offer from other elite teams and Osimhen received a contract extension at Napoli because Osimhen chose to stay at Napoli. But unfortunately, because in the last season Napoli got bad results and Osimhen's performance also decreased but, this moment Napoli still set a high price on Osimhen. Thus, the elite team that currently still wants Osimhen to be hesitant and full of consideration, because the performance decreased last season but Napoli still put a high price for Osimhen.