I feel like it's different on more asynchronous mediums than just chats.
Forums could have thousands of personalities and never really feel dominated by any of them, but IRC channels became dominated by a relatively small percentage of regular users.
Forums can also be small. Regardless of size, one or a cadre of like-minded or easily manipulated folks can dominate a forum.
I think the major difference between forums and Discord/IRC is that the conversations are more likely to be seen on the forums because they’re more persistent and can be more easily referenced to see the entire picture.
That’s certainly not impossible in IRC but it’s more work and less accessible to the less technically inclined.
Forums could have thousands of personalities and never really feel dominated by any of them, but IRC channels became dominated by a relatively small percentage of regular users.