An indie game developer and writer Zoe Quinn dated a guy named Eron Gjoni. They had a messy dysfunctional relationship and broke up. When they broke up, Eron Gjoni decided the most reasonable course of action was to write an 8 page dossier defaming Zoe Quinn and accusing them of sleeping with people in the game news industry for press coverage of their indie game project Depression Quest. Eron then went to a shitload of internet forums and posted the dossier everywhere, actively looking to incite a harassment campaign against them.

Eventually it took root in certain chan spaces and they happily made organized efforts to doxx, spy on and harass Zoe Quinn and anyone professionally connected with them.

Zoe Quinn had some friends in the gaming industry and gaming news industry and when they heard that this was ongoing, they spoke out against the harassment campaign and against Eron, and in turn were immediately targeted themselves, with the chan crews creating accusations of the gaming news media being a cabal of evil gamer hating SJWs wanting to destroy hard core games forever.

This rapidly snowballed into what's now known as Gamergate.