Ideas I can think of are ...
- The glamour and history of success at the club. They're in a relatively low moment but realistically, they will remain competitive in the medium to long term. - - He's young and a long term project could be sold to him.
- The climate
- The opportunity to live and work in Spain could be very attractive, learn the language, culture etc.
- City is his old man's club, might want to plough his own furrow.
- Money. With creative accounting and this potential cash injection from Saudi, they may be able to blow others out of the water for the right player (which for them I think is Mbappe personally).
I think he's obviously got an affinity for City and we're a good option but he's the only one inside his head. Money will be the number 1 factor I suspect.
He can always go to Madrid after spending about 7 years here. At the moment City is the better option for him.