Maybe this is karma for the owner of Napoli who is too eager to get a big title in Serie A and in other competitions such as the Champions League or UEL in the future so he always replaces the coach if he is deemed to have failed to improve the performance of Napoli players since Spalletti's success in bringing Napoli to the top rankings it was a sign that Spalletti's chances were very good in the future but the Napoli owner chose to fire Spalletti on the grounds that he had failed to win a title in the Champions League.
Napoli don't belong to strongest clubs in Europe and they overestimated their power in the past season. From quarter finals, they were not too far from the final match and they hoped to win Champions League. They finally failed against AC Milan and thought it was responsibility of Spalletti then sacked him. However, after one season, we witness that decision was not right. Napoli got problems in this season and they failed to defend Scudetto and have another chance to assess their own power.
We'll see, even if Napoli gets a great coach like Mourinho, Pep Guardiola or any coach who has reliable experience, they will definitely be fired if they are deemed to have failed by the Napoli owner.
I don't know what the owner of Napoli is thinking, who has replaced the coach for the umpteenth time and made the club's situation worse.
Pep Guardiola will not join Napoli because he is on top of Premier League and Europe after last six successful seasons with Manchester City. He will not move to a smaller club like Napoli but it's possible for Mourinho to do this. With Mourinho, there is another barrier for Napoli to sign with him. He is experienced and smart enough to realize problems in Napoli so he will likely wait for chances from other clubs.