Most/all social media platforms generally allow/encourage users to create bubbles and echo chambers. Heck, a bunch of people fled to lemmy from Reddit, because Reddit had started to become more right-wing entrenched with its censorship of socialist / progressive viewpoints and removal of anti-republican content. Ie. they came, in part, to re-establish their ability to have a left-leaning echo chamber/bubble. And in many ways, that's what most of the lemmy content I've seen for the past year has tended to be. Things like Lemmy's options for banning instances, or de-federating 'bad instances', is arguably a 'selling feature' that's basically saying 'you can bubble up!'. Likewise the ability to ban people from communities is touted as allowing vulnerable groups to establish safe spaces, though it also leads to echo chambers -- like it's common to see these stupid memes in threads that basically ask a 'question' that reinforces a community's position, and anyone that challenges/engages with it, is basically violating that communities rules and gets banned. Like posting something about trans-rights in a trans-friendly space, asking why cis people do X -- but if anyone responds in any way negatively about the trans community, even if it's a viewpoint held by a large number of people outside that community, they risk banning, so there's no real authentic dialogue occurring. It's that weird question mark of how to create a safe space for marginalized groups/opinions (be they leftwing or rightwing or whatever), while not bubbling up.

I definitely agree on the communities propped up by single users note -- but I think it's not as benign as you put it. There are people who practically astro-turf communities with biased / ideologically rooted articles. They essentially steer communities to align with their own personal political views by spamming it with their bubble-content. Some of these folks post like 70 articles a day, which, if they're actually reading articles and posting conscientiously, they'd basically have to be doing this sort of thing as a job. It genuinely makes me wonder if that's exactly what it is -- a social media job aimed at influencing public opinion.

Having said that, I think lemmy is not at the size or sophistication to be used as a playground for most corporations at this point. While I see users doing stuff like astro-turfing, it's not easy to see specifically how any one company may be benefiting from what these people are doing -- it feels a lot more politically driven in general, like a single user posting tons and tons of articles about minority rights issues. It could be a campaign to raise awareness, it could be a campaign to force a wedge into a nation (drumming up animosity by highlighting negative stories -- you'd only need a couple 'agents' doing this as a govt to steer things on a lemmy-sized community), etc.... but it's far less in your face than them overtly banning any negative post about product/sponsor X, like you see on reddit. Over there, the manipulation is very overt.