Very important question raised by Dr. Wittner. Then, to answer it, he writes:
"One factor is certainly the public’s preoccupation with other important issues, among them climate change, immigration, terrorism, criminal justice, civil liberties, and economic inequality."
I propose a few slight changes to Dr. Wittner's prose:
"One factor is the media's and ruling class's corralling of the public into activism on issues that, while important in their deepest implications, serve as red-herring distractions from the most pressing crises, which are the war and the runaway speculative black-hole finance economy, which needs war to survive. Indeed many of the other issues thrust artificially to the fore by the media, the political class, and their rich backers (ie. Soros etc.)--such as climate change, third-wave bourgeois feminism, manufactured terrorism--are directly related to and greatly exacerbated by warfare, so that by ending all the wars we would get a good leg up on solving the others."
That's a little closer to how I see it. I think it's interesting, too, that these mega marches don't even address, in any palpably visible way, the other very pressing issues Dr. Wittner mentions or implies: civil liberties, police violence, especially on African Americans, and the pauperization of the masses. That also tells a great deal about the nature of these events, which are shepherding occasions for the neoliberal establishment and therefore have no room for the above themes.
END ALL THE WARS NOW.