Lionel Messi is a GOAT and his playing style is very beautiful and entertaining so having him at any club and league is very good in general. Saudi Professional League under investment and strategies of PIF have wanted to build up their national league bigger and better. They have aimed at biggest star players like Ronaldo, Benzema, Neymar and several times tried to convince Messi joining their league.
It shows their big interests on Messi but there is a fact that times flies fast and Messi in 2025 is worse than messi in 2022 or 2023 by ageing effects. Saudi Professional League and clubs there will receive less contributing effects from Messi in 2025 than if they get him in previous years.
They are not after Messi because he plays good, Ronaldo isn't that amazing neither, but for Saudi league level, he is a star, and Messi would be too, look at how he is ripping the world at MLS. The reason why they want Messi is the name, they want to make some big marketing push towards Saudi football, and they already did that with Ronaldo, before Ronaldo there weren't any big names, after him, there were many other big names.
Messi vs Ronaldo would be insane. More than that, if they somehow convince Messi, and bring him to Al-Nassr, that would be breaking the news all over the world, and would get all of Al Nassr games watched more than probably any team in the world. However, Messi said no to them already before, and will not move obviously.