I didn’t really get why players went to places like China, but in this case the sums are so obscene that you’d have really object to the idea no to go there.
I mean you’re basically talking about making as much if not more than you’ve made through your whole career for the last couple of years of your career.
I think Messi is unique though, he’s probably made enough from PSG and his career to date that a smaller pay day from Miami and a more comfortable location for his family is the priority.