if Napoli get quite a lot of money from Osimhen's transfer. but finding players who have the same level as Osimhen certainly won't be easy. that is what Napoli is worried about. They don't want to sink back after winning the Serie A title after decades of never getting it back. The last time Napoli won the title in Serie A was under Diego Maradona. and now repeated again in the time of Osimhen. so it's only natural that Napoli really expects a lot from Osimhen.
They can get luck one time but it is unrealistic to think they can get it repeatedly. In the last season, Napoli lost some star players like Insigne and Koulibaly but they repeated them by Kravatskhelia and Kim Min Jae. They are both very great successful transfers for Napoli in the last summer. In this summer they already lost Kim Min Jae to Bayern Munich, will they lose Osimhen and Kravatskhelia too?
Will the succeed again with new replacements for those star players? I believe a chance to succeed again is low, else very low.
If they are not careful, they will even lose a position in top four, not only Scudetto.