I doubt very much this is a dynamic of leaders and followers, just not the way that social movements happen in an era of 24 hour news cycles and social media. My neighbors in my working class (but rising) neighborhood see the videos we now routinely capture on our phones, see often for the first time the forms of systemic racism to which they are NOT subjected, and agree that for most of our history and right up to the present Black lives have NOT mattered. A short step from there to print out a sign and put it in the window or on the lawn, with no detour through leaders, manifestoes, or dogmas.