~Snip
I think this might be issues from the board itself, even past manager like Allegri couldn't turn things around for them, who did pretty well before.
I think one reason for their drop is the quality of players they have and the fact that other teams in the Serie A are growing improving their squad makes it more difficult for them to dominate like before when they were having more reputable names as club players. We saw Napoli fighting hard to keep Conte and one of the negotiations the board are giving him aside high pay is the fact that they are going to fund him in order to get top players to the club.
Retaining Conte as coach will basically not guarantee that Napoli will be able to maintain the same performance as this season. Players' performance can easily change and injuries to some key players can change the overall performance of the team. I don't think Napoli will be able to defend their title this season, the same story as last season could repeat itself.
Inter failed in 2 of the last 5 matches, which is clearly detrimental. If Inter can win 4 of their last 5 matches, then Napoli will only end up in runner up position. Napoli were lucky in their efforts to win the Serie A title, but things will be difficult to maintain next season.