Just my opinion, but I don't think that this is Antifa. I think that this is something entirely different.
The suggestion that this is actually an Antifa operation is self-serving, in my opinion. I don't mean the people making the suggestion, who are people of patriotism and good faith; I mean the suggestion itself.
Trump's supporters simply do not find the announced electoral outcome credible (nor do I) and they are demonstrating forcefully that they are withdrawing their consent to be governed by the outcome. They, and we, have to be honest about the entire set of consequences.
And part of that honesty is to make clear that when tens of millions of people no longer believe what the established institutions tell them, and when those established institutions deny the people any other form for redress of their grievances, the people will choose other means of being heard. This isn't about half the nation being "sore losers"; it's about half the nation recognizing dishonesty and having their fill of it.