I doubt it's that complicated, motivated, or considered... It's probably just garden variety disrespectful behaviour. Purposeless agent spam won't be cheap entertainment forever, but you're right that later stages of industrialised abuse will be scary and unpleasant.

Here's the thing. Building trust and then leaving stuff in has been around forever. The fact that it becomes cheaper does not matter that much (since protection against it is also getting better), but it required you to have a bunch of extremely talented people who has spent much of their life diving into given topic. Such driven people are usually even hard to buy, they usually would rather get by with enough income and work on interesting projects with interesting people that get some uninteresting work for tons of money. This still does not stop them from working for Malice. But ethics do. Even if not right away, if people see that what they are doing is not quite OK, the talent stops eroding. People quit, productivity drops. That was a good dynamic. Which now will be gone.

This is exactly what deeply scares me: even IF we get our technical cyber defences fortified within the next months, in a year from now the models will be so good in social engineering that they will be able to extract any information they want.

It's just social engineering. No different than say, 2FA fatigue (blowing up someone's phone with 2FA "is this you? yes/no" prompts until user/child/wife/SO/etc clicks yes) or even just simply harassing IT helpdesk until they reset "your" password.

It's scalable, personalizable social engineering. I think that makes it a lot more dangerous.