Because they didn't have the level of control they wanted, or the mechanisms to prevent being censored they wanted, on other social networks.

Federation allows anyone who finds their ideas censored on one community to make their own. If they get censored from an entire instance they can hypothetically spin up their own instance relatively cheaply. As long as a few instances federate with yours, your content can spread pretty damn far.

All the while, within the bounds of your own instance you control it all.

So it's a combination of reach and control.

they talk about controlled opposition and fbi sabotage a lot

but i am convinced that the various flavors of idiot have one thing in common, which is wanting to put lots of effort into not accomplishing goals, wanting to put effort into stopping others from accomplishing goals, and wanting to guilt others into transfering their effort from goals to anti-goals

tankies are a subtype of the this which is why they overlap so much with genocide joe catchphrase people. who gives a shit if they are useful idiots or just the regular kind

Once we start the revolution and take over the government buildings, we will have full consent of the people, and well if they don't support it then y'know…

They didn't just adopt a fediverse app, they're building one. They could've just built a single reddit-clone that they could rule with an iron fist, but instead they built a federated app, which is equally usable by anyone who doesn't share their views and actively spreads that content to their instance. Why? As you say, it doesn't seem to be for spreading the good word.

It is - in fact, it's Melroy's own instance (which is why it's still kbin, developed by Ernest). He's developing his platform, yes, but it's the ActivityPub commits that I'm interested in.