Sanders coalition is about the only grassroots group that came from the left and was swiftly rejected (twice).

The grass roots movements of the tea party took the Obama era super majority away, and fortified a Trump outsider run.

The boots on the ground every-man on the left is harder to rally, and thus far have not shown any ability to even dominate their own party (their platforms don’t even get taken up by the broader party, just parroted). Plus, if it were possible, there would be a voice in the mainstream media stoking this contingent (as in business has identified an obvious market).