YouTube comment sections are weirdly positive always. It could be a video of some horrible crime and the comments will be about how great the channel is and encouraging the channel to keep making more videos. When j visit actual fan pages anywhere else online there are always a mix of opinions. But youtube is constantly full of obsequious people
What you’re describing just sounds like they paid to have a bunch of bots comment and probably like the video.
Most of the time I’ve seen it, it seems to be more of a parasocial relationship. Even documentary channels have often one or more persons associated with the content which people feel close to. Like, you’re posting somewhere where the creator may actually read it. People probably don’t expect a creator to look into the comment section on Reddit or under a news article. But, it’s more likely in their own channel, many content creators encourage that feeling by actually mentioning reading the comments and sometimes even replying in their comment section.
That’s why comments on many youtube videos are more personal (good and bad), because it’s a place where they can direct feedback semi-directly to the creator.