You probably missed the interview (CNN?) where one of the founders of BLM described herself as a "trained Marxist"
And if the founders came straight out and said they want to push socialism and Marxism as a political idealogy in America they’d rightly be laughed at and left at the fringes of loony left political power. But by attaching themselves to a legitimate social justice issue, they can push their agenda under the guise of racial injustice, thereby giving their extreme political agenda legitimacy.