Napoli never won a scudetto back to back simply because they only won Serie A four times in their entire history but we can't say that it's impossible just because history says so. For me Napoli and Inter have exactly the same possibility to win the Serie A, it's literally 50/50 in my opinion. And Napoli know they have to get more players because they are going to play more matches, and it's exactly what they are doing.
For serie A team only Juventus can win Scudetto back to back and success winning consecutives season since 2011 to 2019, for other team seems difficulty defend Scudetto back to back including Napoli as the winner last season. I remember well how poorly performance of Napoli after winning Scudetto as season 2022/23 but failure finished at top fourth standings one season later. However there are exceptions regarding Antonio Conte as Napoli manager have excellent record with Juventus won Scudetto back to back until six season.
For Serie A season 2025/26, Napoli prepare teams quite well behind not selling any key player last season and success signing top midfielder Kevin De Bruyne from Manchester City, now completed player having by Napoli and interested to know mission for winning Scudetto back to back will easily or not. Get bit difficult for defending Scudetto next season because last season only played at domestic league in this season Napoli have busy schedule matches by playing at UEFA Champion League.