Conte might have his reasons for rejecting the offer and they will have to respect his decision.
I think Conte wait for the offer from Juventus. There was a rumor that Juventus will fire Allegri and replace him with Conte. It makes sense if Conte prefers to join Juventus because he ever succeed with Juventus. He should have a bit intention to succeed again with Juventus in the next season.
Mazzarri is the better and probably the best option for them.
Can you explain why Mazzarri is the best option?
Honestly, I don't find a reason why Mazzarri is the best one. I think Mazzarri is only an alternative coach.
I think Mazzarri has time until the transfer window in January if he can't make any changes then I'm sure he will be fired too, I understand why many coaches reject offers from Napoli or clubs from Serie A one of the reasons is that most of the clubs in this league are experiencing a financial crisis so they don't have enough budget to bring in players while the coach certainly wants to bring in several new players to help implement his strategy.
Agree. If Mazzarri can't improve anything, he surely has a chance to fire by Napoli management. But I assume Napoli management will give him the time until the end of this season. I doubt whether Napoli can get a better coach when the season is not over. They must be patient with anything happening with Napoli under Mazzarri's management.