Honestly, before now, this is what I had implicitly assumed was going on. I'm not American, and I had blocked most of this trash when it was happening, but my impression was that these ignorant people were just "coming out of the woodwork" so to speak.
Of course, fear and hate are learned behaviors, but it's interesting to me to see that these people were actually being quantifiably radicalized by that website in particular, and they weren't simply bringing views to the platform that were being established elsewhere.