I also have a personal belief (not supported by any evidence) that a lot of the gamergate movement was actually just a bunch of kids: internet trolls and griefers with nothing better to do, who just see this as a giant game they could play, something mischievous they could do without getting caught. Even if this is true, it doesn't make the situation any less serious. There were still plenty of non-anonymous adults standing up for the movement and rallying those troops.
Depends on how closely you bind your definition of kid to actual age. Legally, most in the crowd were of the adult age. A high but not quite majority percentage were in their 30s, with the slight majority fitting into the 20-29 side. I'll have to find the research into it again, but it was depressing to see.
I also realized mush of this thread has been discussing this as if it's in the past. Gamergate is still a thing today, and still causing problems for many people.