and had deep Groyper community ties

Again, I don't think these assumptions are going to age well.

There's no evidence he had "deep Groyper community ties." There's evidence that he did some meme-y stuff - but memes propagate all over the place, especially among young people, and trying to establish "community ties" from the fact that someone repeats a meme is a fool's errand. The Helldivers 2 speculation is especially foolish, since that was one of the best-selling video games in the year it was released.

And what little we know of the suspect doesn't mesh with any strong Groyper affiliation. He doesn't appear to have had a large online presence. He appears to have been accepting of trans people (Groypers are anti-LGBTQ).

Dude might not have been left-wing, but I don't think there's a high probability that he was a Groyper or that his killing of Kirk had anything to do with the Groyper-Kirk conflicts.