I'm sure he also wants to break Higuain's record and also wants to collect his accolades from Juve supporters after doubling our CL trophy after a long wait (he'd be worshipped forever), and win more league titles.
He's all about individual recognition.
Might also feel he'll last longer playing in Serie A when, in reality, he'll get kicked more.
And after winning 3 CLs in a row with a team, it's a motivation issue at Real (plus not feeling respected enough), and we're a better team than United (not a fan of Mou either) or PSG.
Just never thought we could afford his salary before the rumors. Forgot how insanely marketable he's. Ferrari/Exor will happily pay his and sponsor him.