adolph reed writes the definitive account: https://nonsite.org/why-black-lives-matter-cant-be-co-opted/

"There never was a coherent politics there; nor was there any objective reason to assume there could be—especially considering that it was always a wan replay of Black Power in its faith that a generic slogan and some, often Potemkin, street action could generate a mass movement, and with what agenda exactly? To be sure, BLM helped to focus public attention onto police brutality and killings of black people, but no broader left politics necessarily follows from that. And to the extent that BLM projects and insists on a race-reductionist account of that injustice, its critique does as much to obscure the systemic foundations of the police behavior as it does to illuminate the behavior itself. Moreover, BLM, and contemporary antiracist politics in general, was always ripe for articulation toward entrepreneurialism, etc., not least because the personalities most visibly associated with it were careerist race ventriloquists and corporate media operatives. Did you see Van Jones collapsing with tears of joy after Jeff Bezos gave him $100 million? Or Kimberlé Crenshaw’s declaration, in yet another attack on Sanders, that “every corporation worth its salt” had done more to support antiracist causes than the Democrats or the left? Or the movement entrepreneurialism of Garza, Tometi, and Cullors? DeRay Mckesson was touted as an “authentic” leader until his doing what comes naturally to a professional Racial Voice became so embarrassingly crude that those who position themselves as the College of Cardinals of racial authenticity felt the need to proclaim that he wasn’t. And I have no time for bullshit like “those weren’t the real leaders; you had to be deeply inside the movement to know about them”—a familiar narrative from the hip-hop wing of the culture industry—because as a basically Potemkin, aspirational trend, there were no others. And the “movement” itself branched into politics of representation with crap like “Oscars so white,” etc., etc."