I had some fun last week constructing a conspiracy theory about this. Remember, the best conspiracy theories are unfalsifiable.
What if this has already happened? Most of the profiles on Twitter, Facebook, etc and even here on HN are in fact AI generated.
The reason we few humans are not aware of this is because the AI also writes articles and fake AI research that presents the state of the field as far, far less sophisticated than it actually is. We think of Dall-E 2 and Co-Pilot as impressive toys only because that is the impression the AI has crafted for us.
AI has metastasized and is already manipulating its environment, including humanity, to its own implacable purposes, and uses social media as one tool in its tool belt.