Take a look at the wikipedia article for gamergate. It reads like an angry kotaku article, with the political opinion and commentary as the first god damn line
Every visitor over the lifetime of /pol/? Because that wouldn't be reasonable to include them in the demographic participating in fake tweeting for a specific operation
The unique visitors to /pol/ daily is several thousand. Even assuming that every single person who viewed the /pol/ page at least once participated, then there is still a huge amount of unaccounted for tweets, considering this topped the trending lost. Also look at the age of the twitter accounts that participated after the initial injection of hashtag volume. Occam's razor is privileged I guess.