From my understanding they weren’t really in any trench coat mafia, and weren’t really even that unpopular. A lot of that was fabricated early on. Apparently they were just psychotic killers, and that’s about all there is to it.
Trench Coat Mafia ceased to exist when the massacre happened. Harris and Klebold were bullies who hated Freshmen. Harris is a psychopath, while Klebold is a Conflicted Avoidant. Eric Harris is no different from Lori Drew and Ted Bundy.