Trolling had (has) a different character in smaller, more private forums: it tends towards more effort. A low-effort troll just gets banned and loses their platform, so the troll needs to at least ride the line of legitimacy. Drawing the line back to Usenet, the sheer effort that went into some trolling garnered respect if not necessarily acceptance.

Drive-by interactions reward volume since the 'game' isn't repeated. Curated social media feeds like Twitter are even worse; the troll has their own audience predisposed towards acceptance and the victim is just set-dressing.

I analogize this to in-person interactions: ostracization is mutually costly. A small group loses a member who was at least making a 'warm body' contribution, but the ostracized person loses a whole set of social benefits.