If you'll indulge some conspiratorial thinking on my part:
In the past decade, powerful groups all over the world have realized the importance of presenting their viewpoint (read: propaganda) over social media. Numerous online "reputation management" firms have been born from the existing edifices of marketing and PR. People like Elon pay big money to have a combined-forces army of humans and bots pushing their views in every online venue imaginable. LLMs are the newest and most potent tool in their arsenal.
This is compounded by the genuine human users who, once they have been sufficiently propagandized, will start to participate in this effort unknowingly.