Check out https://zulip.com/for/communities/ and some of the linked case studies; they explain it better than I'll be able to in a quick comment.
But the main reason is that the topics-based organization and ability for moderators to move/split conversations means one can read and participate in a community much more fully given a fixed amount of time.
But the main reason is that the topics-based organization and ability for moderators to move/split conversations means one can read and participate in a community much more fully given a fixed amount of time.