Because they want people to get frustrated with the internet and stop using it. People were banding together and finding out things in common. So they poison the well with thousands of bots and shills, so everyone gets upset and learns nothing. Thus regaining control over their communication network, like they had with TV. Unfortunately the only working response to this is to create a walled garden forum, but that also implies a high degree of censorship, which is antithetical to uncovering taboo information.

So it's kind of this weird lose-lose situation and no one has figured out a solution yet. And it's only going to get worse as bots get better at seeming human. The internet will be 95% bots in probably 10 years. It's probably 50% on a lot of forums already.

It's honestly a disaster for humanity because a lot of people mistakenly think it's real, and a real reflection of how humanity thinks and acts, but it's fake. And it makes people depressed, disconnected, and despondent to see this and think it's real. Which is also useful to those in power, because if these attitudes are held deeply by the populace, it disables people from wanting to change the world because they think it's useless.

Seems offline communities will be the way of the future as the internet becomes increasingly poisoned by bad actors that are nearly-impossible to defend against. Video content is more likely to be real than text content these days, but even that will come to an end as deepfakes and video editing improves. In real life you can at least verify you're talking to a flesh-and-blood human being.