The Iraq War protests were some of the largest in history, and they accomplished exactly nothing (and to your example, look up Malachi Ritscher). Occupy Wall Street was a massive movement and accomplished nothing. The protests against Obamacare repeal were massive and widespread, and seem to have only succeeded in delaying the destruction of Obamacare to the current tax bill. Black Lives Matter is a massive movement that has accomplished meaningful change in a few jurisdictions and nationwide has managed to at least generate conversation, but that conversation has already been largely derailed to the question of whether or not football players need to stand for the national anthem.
Office holders are not beholden to people yelling in the streets but to the people who get them elected. This means the people who show up to vote and, increasingly, the people who finance their campaigns.