I agree with you, there is no way he could have done something without a trigger that made him do so, but wrong is still wrong no one can justify something that is wrong.
I don't know exactly what happened, but from Ronaldo's habits I can judge that there is a trigger that makes him do things like this. I see him very respectful of others if others can respect him too, or in other words respect each other. But when something makes him angry, he will respond too, and actually I'm not surprised when he responds with something "excessive" because he has that kind of character.
Perhaps we remember when Atletico Madrid supporters mocked him, he immediately responded with a celebration when he scored a goal. Likewise, he responded to the celebration made by the Atletico Madrid coach when he scored with the same celebration.
After I searched various sources I couldn't find a real reason why Ronaldo became very angry because some media were exaggerating the news, but from several sources I read someone said that initially Ronaldo was called Messi, after that other news sources said that Ronaldo was called Messi, Al Hilal fans threw scarves at him so he felt like he was being harassed.
These two causes make a little sense but still for me Ronaldo doesn't need to do it because it's too risky or if not he could be deported from the Saudi pro league for harassing other clubs.
Maybe I don't really like Ronaldo, but I justify Ronaldo's behavior because he only seemed to defend himself when he was being harassed by Al Hilal fans, so if he was threatened with deportation, it wouldn't be possible because there were reasons that pushed him to do something like that. .
I hope this is the last time Ronaldo behaves like that because it will really harm his career if he doesn't respect other clubs.
I'm not going to justify something that Ronaldo did as I said before, wrong is wrong. But in this case we also can't blame one party. The supporters who did it were also wrong and in my opinion should be given commensurate sanctions so that the same incident does not happen to other players.
If he is shouted Messi's name, this is actually not something new for him, in fact he is a person who often gets that treatment. But what made him more emotional I think was because there was a throw made by a supporter, even though it wouldn't hurt him, but that was one of the actions that in the end he overreacted like that.
As I said, both sides should be sanctioned, both the supporters and Ronaldo, because both are wrong in my opinion.