Luciano Spalleti was the background problem that started affecting Napoli’s team, he started using selfish interest in making his selections, the management sacked him and signed the new manager Walter Mazzarr.
The new manager is yet to get the complete stability of the players which is why their performance was not in good shape, but as it stands now, he has started gaining momentum to move the team to the level they deserve because Napoli did not belong to the bottom ten in the Italian Seria A.
As far as I remember, Luciano Spalleti was not fired from Napoli but instead resigned. Leaving when he was still successful was the most beautiful and happiest thing, rather than leaving when he was down, let alone being expelled by the club. In fact, the choice to withdraw from Luciano Spalleti is a good choice because we see coaches Pep Guardiola at Barcelona, Zidane at Madrid, Sir Alex at Man United, and perhaps many other examples of coaches. They will be remembered for their greatness, not because of their failures, they will be remembered not just for a moment but for all time.
The same thing is happening to Napoli at the moment, after Spalleti resigned, Napoli's condition is getting worse and they have changed coaches several times, but this has not made Napoli recover. However, now Napoli and coach Francesco Calzona are starting to recover, especially after the big win over Sassuolo, Calzona's test will continue when he faces Juventus this weekend and against Barcelona in the second leg of the Champions League. If Napoli manages to win this big match, perhaps it could be said that Calzona is the right coach to replace Spalleti rather than the previous coaches who were fired.