Channels get shadow banned by activists through manipulation of automatic moderation. This required keeping the activity under the threshold needed to bring a human in the loop. It's been a while, but there are guides on dark web forums on targeted harassment and manipulation of auto moderation of various platforms.

It's always frustrating to see non techy creators wail and gnash their teeth about being banned or harassed by a platform, when it's a million times more likely that a small group of dickheads manipulated automated rules using downvote and channel reporting features.

Not sure why captcha or other barriers aren't required for the use of abusable functions on social media, that's always seemed very user hostile.