Because they're not being fired up by democrat politicians to burn down and loot cities. It's just like everyone says constantly: Black Lives only matter during election years.
I find it interesting that support is at an all time low because there's been no msm news worthy stories to report.
I feel it kind of disprove the point that this article is making that they had a much higher level of support while "burning down main street".
The squeaky wheel gets the attention I suppose.
I would actually disagree with this interpretation. If you look at the poll, republican voters, which make up a larger demographic, went from -50% to -83%.