They (not Trump of course) had to walk it back when it turned out not to be true.
Is there some outside groups posing as others, possibly, but to blame a majority of problems on them is just BS.
I see a lot of mischaracterization of what is a category, not a group. From what I can tell antifa is anti-fascism, and somewhat characterized by people willing to take direct action.
https://www.berkeleyside.com/2018/08/08/eric-clanton-takes-3...
How he didn't get 7 counts of attempted murder is beyond me.