"I was seduced by the project and by the people involved in it," he said.
"I have talked a lot with [director general] Julien Fournier and the president [Jean-Pierre Rivere].
"When I look at the squad, it makes me very envious. There is everything you need here to succeed.
"My playing career no longer counts for anything, it's part of the past. The important thing for me is to have a clear idea of what I want from the players, a precise game plan so that they can express themselves because the talent is there."
Nice finished eighth in Ligue 1 last season – just a point outside the European places.