Never say never when it comes to football. If Napoli were able to win the league trophy last season tell me why it is impossible to win it this coming season with the recruitments they have made to further improve their team. I think it is very possible, their team looks very organized and stronger for next season.
Napoli will have a lot of busy schedules and that will affect their performance. Unlike, last season that they were only focused on Sera A competition. This is one of the reasons why I don't see them capable of winning the Scudetto back-to-back. Fatigue and injury will always play their own role on the players. Napoli was lucky last season that none of their key players was injured.
Last year, sorry, last season, we can say that he managed to win by using luck and taking advantage of Inter's mistakes. This year, we don't know; it could happen the other way around. Another team could be waiting in second place and steal the title from him at the last minute. Last year, it seemed like Inter would win everything, and instead...
That's football, sometimes it's not the team that plays best that wins the title, but the one that makes the most of the opportunities that come their way. That's what Napoli did last season. Inter Milan were initially closer to the title, but in crucial matches, they dropped points, and Napoli capitalized on that.
Napoli is currently on a good run; the foundation they've built shouldn't be lost, especially since they still have the coach who led them to the title. However, the ups and downs of a team are unpredictable, so we'll have to wait and see what happens next season.