Well I would imagine many of those who acting this way have always had sympathies for the underlying ideologies of China and the USSR. Liberals are a small minority after all.
I wish so but I'm not so sure about that. Harvard CAPS had a poll that showed more than half of the young people support Hamas. The Squad have been steadily gaining popularity, so much so that a recent article in Spectator asked who would be able to stop the Squad after the Biden administration is gone while Pelosi already stepped down. And in multiple cities in the US, the mob destroyed statues, yet left Lenin's intact.