When one considers the factors that actually get people out into the streets like in Sri Lanka, they're essentially only economic. People have a comparatively much higher tolerance threshold for sociocultural rot; but if they're economically suffering, their tolerance quickly wears thin, a la the Weimar.

Now, who is least likely to be economically suffering of the mentioned groups? I'd wager that 'Graduate Degree' greatest correlates with higher living standards. These are the people whose earnings are high enough that they can afford to take a hit, and thus can afford to preserve their Left or Far-Left beliefs in the unfortunately common event that they harbour them. But the '19-29' and 'No College' groups are, conversely, on the frontlines of the economic troubles.

I think the persisting black support is the one that raises questions, because that clearly doesn't correlate with higher living standards. In their case, however, I'd wager that it is because they are far greater beneficiaries of the current order of things compared to the other groups. The system is geared towards them—especially its deep opposition to the various structural, institutional -isms and -phobias of which they believe themselves to be victims—in a way that it simply isn't for the other groups. Notice that ageism (a term many probably haven't even heard of, much unlike 'racism') and discrimination against the less educated aren't considered anywhere near the issue that 'racism' is.