I think the idea of automatic promotion to trusted status comes from a place where forum members are mostly well-behaved, and where bad actors will not naturally last long enough to reach the higher levels.
In a forum of mature adults, or a forum that’s part of a company or a shared endeavour, this seems to me like a good model.
In a forum of less disciplined people, or in a space where hostile people might join up and work hard at being destructive, it’s not so good. In these cases, the forum admins should set the thresholds to put things out of reach, and use manual promotion (and demotion.)
The automatic and self-regulating nature of the automatic promotions and demotions: as your forum gets bigger, it automatically gets more moderator-like attention.