I'm gonna make an attempt to see if I can do it without bias with my very limited knowledge of it just to see how it goes.

GamerGate was a social media movement/protest/reaction of sorts that showed up during the ramp up of irritation over the topic of people talking about women in gaming. It was a hot topic with lots of coverage.

At some point, a game-maker released a conceptual indie game that seemed to be in that weird spot where games writers tend to be positive, but a number of avid gamers didn't find it remarkable. So, it got positive reviews, but some gamers were confused as it didn't match what they felt.

The developer of that game had an ex-boyfriend that wrote a really long post about her that was negative and mentioned a romantic relationship with her and a Kotaku writer. He didn't review her game, but the idea of her trading sex for a positive review popped up in the crowd's narrative. Another writer said the ex-boyfriend structured his post to hit the hot buttons that would get gamers fatigued with women-in-gaming topics on his side about his ex. Whether or not it was intentional, it hit a lot of hot buttons that resonated with a certain crowd: dislike for Gawker media; short and conceptual indie games that got a lot of press, but might not be fun as games; short indie games priced at $10; a feeling that gamers should like or support a game more because of a female dev; feelings about consumer journalism and whether it was consistent; feelings about women getting special attention and then adding the perception that someone could use sex to get better reviews when a male couldn't. People will fight all day about whether each of these are true, but these seem to be elements that strike the nerve whether fair or not.

The moral highground argument that people gathered around was "ethics in journalism" since the perception was that a lukewarm game that they felt was overpriced got a lot of hype and good reviews because of a developer's romantic relationship with a writer. The real story isn't clean cut or in that order, but that was the perception in the middle of it and that was the rallying cry. However, that brought a lot of bedfellows that had a whole mix of venting they wanted to do about the topic of women in games, arguments about misogyny, feeling browbeaten over a hobby, etc. Not all the bedfellows were the most constructive human beings and so you got the mess of ugly attacks and Internet death threats that show up with these things.

One argument from the other side was that while ethics in journalism do matter, why was this the one situation that set everyone off. For example, you can find lots of evidence of journalists grabbing beers with people they review, taking gifts from game companies, being flown out to junkets, etc. People have griped about these, but it never hit the same crescendo.

So, like anything online, people who jumped in with a moral cause that they saw initially based on the evidence of the moment eventually got fatigued by their own bedfellows and the muckiness of it and just kinda dropped out of the conversation. There were diehards following, but it didn't contain the full crowd that initially showed displeasure with the situation.

It seems you can find people who remember it differently from either side. Some see the GamerGate enthusiasts as sort of redpill types caught up in misguided misogyny and others see it more as guys who were never fairly heard out as "PC culture" wouldn't allow them to talk about it the way they wanted.