I think you are not being fair to Cristiano Ronaldo in this case because there is definitely nothing disrespectful if Ronaldo decides to join Al Hilal from Al Nassr. It is not right to miss emotions with career because Cristiano was never a liability to Al Nassr, rather he helped the team and they surely made money from him through advertorials and other ways he would have brought traffic to the club. If he decides to try another club, nothing stop him from doing that.
He can try other clubs but it shouldn't be in the same league as that'll be disrespectful to the club he was playing for already. He tried to do the same thing when he wanted to join Manchester city but Manchester United didn't allow that to happen so they bought him when they didn't need him and it ending was bitter for both sides. The same thing might happen to Al Hilal. Not evey player that joins the rivals of his former clubs does well and Ronaldo is now too old to be taking those kind of risk before he spoils his football career among fans. I don't think Ronaldo is interested in any trophies that isn't international but what he's chasing now is his goals record.
In essence, Al Hilal managed to consistently get trophies without fancy players because after all, despite the fact that Al Hilal had Neymar but Neymar also only suffered injuries throughout the season. So, I think Al Hilal doesn't really need Ronaldo to get trophies, but Ronaldo himself needs trophies so is willing to join Al Hilal. Despite the fact, if for example Ronaldo plays for Al Hilal I believe there is no guarantee for Ronaldo to get a trophy there. So, if for example later Ronaldo plays for Al Hilal and then Al Hilal becomes a team that fails to win trophies, then it will be a bad judgment for Ronaldo himself, at least it will be a risk and or consequence if for example Ronaldo joins Al Hilal.