Unmoderated forums also lose users to moderated forums, because nobody wants to sift through a pile of trolls, nazis, pedophiles, etc. just to find something on

Unmoderated forums also lose users to moderated forums, because nobody wants to sift through a pile of trolls, nazis, pedophiles, etc. just to find something on-topic. I have seen it happen with Usenet, with any number of loosely moderated mailing lists, websites, and so forth. Users want some degree of moderation, and advertisers are going to gravitate toward the platforms with the most users.