Ronaldo has a few hidden clauses in his contract. He is guaranteed of additional payments if he stays in Saudi Arabia until the bidding for the 2030 FIFA World Cup gets finished. There is no guarantee that Saudi Arabia will be able to win the bid, but they believe that presence of Ronaldo is going to help them immensely. The Saudis actually want Ronaldo to forfeit his Portuguese citizenship in exchange for a Saudi passport, but from what I have heard his family is against the idea of settling down there on a permanent basis.
The Ronaldo family thinks Saudi Arabia as a business field only and not a place where they could settle down for good, after all, they are more accustomed to their own tradition in Portugal and so that's where the whole family will live after all of these businesses are finished. 2030 bidding might be Cristiano's limit that is why they are granting him additional payments because they need his influence to help the whole league win the bid and after that, Cristiano can retire for good from the football field.
Admit it or not, the main factor for Ronaldo to play in the Arab League is because of the money factor, not a football passion factor. It is undeniable that at a young age a player only plays for the passion of football, at that time they didn't really care about money. When entering the end of his career, they do not care about the passion of football because they want to collect some money before retiring.
Ronaldo will never give up his nationality to accept Saudi Arabia's offer, he has contributed greatly to Portuguese football and will be remembered as a proud legend of Portuguese football. Ronaldo as a newcomer to Saudi Arabia, he will stay there as long as his business is running smoothly. After that he will return to his country to enjoy old age after completing his career in football.