It is about playing competitive football rather than enjoying money which is a little bit surprised.
Modric is a good player and understands that if he leaves Real, his career will end at an unknown club... That's why he chose to continue playing at Real... Nothing surprising about that, money is not the main thing in everyone's life... As for Saudi Arabia, it is interesting to see how they try to attract top players from different leagues to their country... But it seems to me that it won't succeed anyway... They just have a lot of money but little skill...
Also, contrary to what you said, it's actually working for Saudi Arabia, there is a revolution going on everywhere, must it be other countries/leagues alone? Their strategy is working as people are now following and viewing Saudi League more than ever, and even streaming companies have increased, which includes journalism and means more money and relevance for them.
It's about what people value, and with the look of things, they are valuing the league because of the stars they are wooing there.