Disinformation campaigns don't mean all such activity is by political shills.
[1] https://www.nbcnews.com/politics/justice-department/law-enfo...
How do we actually know this?
Or to put it differently, how much do we know about the interconnections of such groups? I'm sure that some are just kids who like the look & dress up with their buddies (no connections). Some seem pretty organised. How do we tell the extent from outside?
I would hope there is effort put into infiltrating and studying such things. But presumably any serious FBI or whatever effort isn't going to be keen to spell out how they know what they know. (IIRC this was part of what broke up the KKK, that and anti-mask laws. Which at its height was also a mix of fairly organised & not at all, although I don't claim the same mix.)
We don't which is why it's weird the current administration is trying to declare 'antifa' a terrorist group without presenting any real evidence. If they know something we don't this would probably be a good time to tell us.