So I’m not going to speculate on the exact inner workings of the trust system, because 100% they are being kept vague so people don’t try to fast-track themselves to trusted.
I will say that when I’ve moderated games forums and servers in the past, we awarded the equivalent of a trusted status to people after they had been around for a bit and active without causing trouble. It was much less about someone’s popularity (ooh, so-and-so has 100 likes, we have to give it to them now), but much more about someone demonstrating the ability to participate in the community without violating rules. “Trust” is not about rewarding popular people, but about making it harder for people to drown the forum with burner-account trolling.
If I were setting up a trust system, that would be how I’d go about it. Can’t speak for Blizzard though.
[ed. To say it another way: The trust system is likely geared to reward responsible forum users, rather than popular forum users.]