Rudi Garcia has been sacked, they called back Mazzarri after 10 years.
Conte is rumored to have refused them, twice.
Finally, Napoli fired Rudi Garcia.

It makes sense, Rudi Garcia never improved Napoli performance. We even heard a rumor about bad relationship with the players. This will have no solution, firing him is the best decision.
I'm surprised Napoli hired Mazzarri. I think there is no very special thing with Mazzarri when he was the manager of Napoli in 2009 until 2013. The only thing that he can achieve with Napoli was winning Italian Cup in the season 2011-2012. But Napoli may have no alternatives for the coach, so they decided to sign Mazzarri.
It is very unfortunate Conte rejected the offer.

Conte might have his reasons for rejecting the offer and they will have to respect his decision.
Their decision for signing Mazzarri would not just be looked into from the negative aspect of it for not being able to win a trophy with them in his past seasons in the club but just only the Italian cup. This could be a changed Mazzarri, better and improved than the former one.
Napoli are currently in need of a good coach to push the team forward this season, their want won’t make them to settle for less when making a decision of a manger to head the team to success this season. Mazzarri is the better and probably the best option for them. He got a new team and new player’s different from the ones he once managed before, these ones can give him better what those in the past might not give him. He just needs to get to work and revive the team’s winning spirit again.