When a community I'm part of moved from Usenet to a forum around 2007, I remember a few technical points that persuaded members, mainly easier moderation and post editing.
One troll in a community of 200 has an outsized impact.
One Usenet killer feature that was lost in web forums is the per-post read/unread status, which made long-running subthreads manageable, decoupling them from each other. In web forums you only have "up to page xy" read/unread status, which forces participants to follow threads linearly and thus decreases asynchronicity and makes parallel subthreads hard to follow.
