Nothing of what you mentioned. Neither Gila neither CL is the reason why he won't go to Milan.
He's from Brasil, he has no feelings for Juve and Milan. His favorite team is probably some
Flamengo de Sao Paolo Gama.
What he wanted was more money and better deal.
Stop being naive and romantic, hoping that Juve fans will play for Juve.
Why would Amauri care about Juve or Milan or Inter ? He doesn't have any feelings just like Chiellini won't have any feelings for Flamengo or Corinthians if some day he's going to sign for a Brasilian team.
Personally he may have hoped to sign for Milan rather than signing for Juve, but it has nothing to do with him being a Milanista. He'll be a sure starter in Milan, playing alongside many Brasilians. That's why Milan were more attractive.
But if you guys take that as something bad, then...