While there were bad results, Napoli changed the coach in order not to get worse. Of course, it would have been better if he had not changed it, but we do not know the results of the matches that will be played. Maybe if the coach had not changed, worse results would have been achieved. That's why they wanted to evaluate this possibility, I congratulate them on this. Actually, I think they did the right thing.
I thought the management of Napoli would have allowed Walter Mazzarri to continue with the club till the end of the season because changing a coach now might have some negative effect. Francesco Calzona might not be a bad replacement but he would need time to understand the players which will aid in getting good results. An example is what happened in Bayern Munich where Thomas Tuchel will be allowed to be in charge of the Bavarians until the end of the season. Napoli was not impressive in the round of sixteen game against Barcelona but they were lucky to grab a win. The club was outplayed throughout the match and they showed less sign of winning the game. They will have a battle to get a win in Barca. But before then the new coach will have to prove that he is the right replacement when they meet Cagliari, Sassuolo, Juventus, and Torino.