Amazon probably outsourcing to a PR that specializes in union busting.
But the PR firm that has little technical expertise - they just know they need bots to do some astroturfing.
So the PR firm outsources to an IT consulting firm.
But the IT consulting firm only bids on contracts, they don't do the actual work, so they find a subcontractor.
The subcontractor may hire subcontractors. Continue this step for however many iterations the value of the contract will allow.
Eventually the subcontractor hires a gig worker or an underpaid staffer to do the minimal amount of work possible.
The gig worker avoids as much effort as possible, because they're paid by volume rather than time.
At this point the requirements may or may not be fulfilled, but the admins of each org are satisfied, so they move on to the next contract without verifying the work.
Edit: I wrote this facetiously, but u/SpaceNoodle found a news article suggesting at least some of these accounts are legit, as backed up by a Belling Cat investigation.
If Amazon wants better astroturfing from the gig workers, those gig workers doing the actual work need to get a much bigger chunk of the money. They should unionize!
There's no reason to try any harder than this. Most people who will see this tweet won't look at the handle or the replies - they're read the tweet, then move on. And if they see enough of these tweets, they may just internalize the notion that unions aren't worth it. It's better for Amazon to make more tweets than it is for them to make better tweets. And it's not like they're going to see any repercussions for trying to maliciously influence their employees.
Something similar happened when there were all of those news stories about abusive work environments at Amazon. Amazon employees spontaneously tweeting about how much they loved their jobs.