The popularity of the Saudi Pro League increased drastically after Ronaldo joined Al Nassr, and I think for that reason, they are still keeping Ronaldo, even though he's no longer young. Al Nassr hasn't won a trophy yet, but Saudi initial goal of recruiting Ronaldo seems to have been realized, and maybe this season Al Nassr will succeed in winning the trophy.
He is only a first super star player joined the league and lays first foundation for Saudi Professional League growth. It has been three years since his transfer there and the league has still been growing with several star players joined in this summer transfer season. I believe that Saudi Arabia already got a good strategy and they only need to maintain it for like 10 or 20 years to harvest succeesful results at national team level in World Cup tournaments.
Overall, the PIF has laid a strong foundation for their long term goals, with Ronaldo, the Saudi Pro League has become better. I think former top European players have the courage to move to Saudi because they see Ronaldo, which means Saudi can also offer a good environment for football, even if it's not as competitive as the top European leagues. Of course, the main attraction for them is money, and that's actually also generally true in Europe.
Strategy and investment fund from PIF make the strategic growth of Saudi Professional League is different than what China had with Chinese Super League years ago. This makes Saudi Professional League growth more sustainable than Chinese Super League project and by maintaining their investment in the league, appearances of star players in the league, it can help domestic young players more time and chances of training and playing with world class players. In long term, like after 10 years, it can help Saudi Arabia having a new player generation at higher level and comes nearly to world class level.