Go look at their content. Most of them aren’t trying to spread communis. If they believed in it they’d be trying to persuade others of their views, but its much more common to see strawman attacks and low effort group think.
Of course, I don’t have secret Kremlin or CCP files to share with you, I’m not sure how else I could prove it. No doubt you’ve seen some of the posts of “Trump supporters” happily offering cooking instructions when requested, or claiming to be a gender/race they obviously aren’t.
The Kremlin and CCP are highly active spreading propaganda through anonymous social media, and they’re absolutely here on the Fediverse with its sporadic moderation.