While osimhen played a huge role in Napoli trophy win i don't think we can say that they won't be able to win the serie A because there is no team that are ahead of others in the serie A so there are a few who can win the title such as inter juve milan and napoli, even teams like roma and lazio might have a small chance this is how close the teams are in term of level i think as long as napoli team secure a decent striker they have a fair chance to be champion again.
Next season is likely to be even more exciting in terms of the title race in Serie A, even though the Napoli team can secure their best striker. Because if the Napoli coach is not so consistent in making his tactics or strategy for the next season, then Napoli will have a little difficulty competing with his rivals. Now everyone has seen how Inter, Juventus, Milan, and Lazio did last season so they can all make even bigger surprises next season in Serie A.
Napoli's journey in Serie A, in my opinion, will not be as easy as the previous season. Apart from the change managers, other top teams such as Inter, Milan and Juventus will make specific improvements to conquer Serie A next season.
New Napoli manager Rudi Garcia will need to attention to the development of their Serie A rivals to adapt to other teams. But in this case Napoli are one step ahead in confidence than their rivals