Benitez succeeds Walter Mazzarri, now of Inter Milan.
"Rafa Benitez was the right candidate for us," ADL told a Press conference. "He has international experience and we can grow with him.
"An eight-year cycle has ended, and now we begin a new era.
"We have a great relationship with Edi. He knows that Napoli is a big stage. It is only human nature to be interested when big clubs like Real Madrid, Barcelona or Bayern [Munich] say they are interested.
"But here he can be a prima donna. At Real Madrid he would just be one of many.
"Manchester City are not willing to spend [Cavani's buy-out clause of] 63m on Cavani."