A big reason for this is that left spaces need to be very tightly moderated in ways that right wing spaces don't need to be. Part of that is because left spaces are going to disproportionately represent bipoc folk, queer folk, disabled people, etc. And they're not going to stick around in spaces where they have to constantly defend their own existence. It's already enough of a hassle in daily life, so why go on a forum that's full of slurs or go to a nerd con that's full of smelly dudes who'll say you're the incorrect race to do cosplay? So people drift away, find their own communities where they feel safer.

Right wing spaces have the privilege of speaking to the dominant ideological authority already. Unless they're pulling out actual Nazi flags or doing salutes, they come across as fairly normal to everyday, uninitiated people who don't think about theory all day. Whereas leftist perspectives in the west aren't as common, and usually at best it's the very milquetoast progressive liberal sort of stuff. You say there's not enough leftist voices to frame the narrative within gamer communities, well there aren't much in the way of leftist voices in general. It's becoming more common to express anti-capitalist sentiment, and thankfully among younger people, but it's still fairly rare within the west and English speaking spaces.

Yeah, so the right already has the home field advantage here. Modern nerd culture can be traced back to things like Star Trek conventions in people's basements, or ham radio enthusiasts. It started off with moderately affluent white guys who had access to Usenet in the early 80s who were prime targets for the burgeoning commercialism of little plastic trinkets. It was only a matter of time before those beginnings would coalesce into functionally coherent fascist rhetoric because of the inherent overlap with the social base for white, settler fascism.