but politics having an excessive focus on videogames isn't really natural.
Ok, this one is fair
As I understand it though, Mélenchon's team has just a far better understanding of Internet than the others, and so he showed some interest in a lot of meme stuff (Khaled Freak remixes notably), which in turn engaged the community which started developping things like the comic and the video game. The all Discord Insoumis thing is impressive, it's pure activism organised by people outside of the official team, but they actually managed to develop a lot of different projects. It's never his initative, but he's embracing the work of people who support him.
Regarding video games in general, he met some of my friends at their VR studio, and they have been really clear that he has a genuine interest in video games. While I was in school with them at the national video games school in France a few years back, we received a lot of politicians so they have a real point of comparison.
With time and experience when someone is making specific proposition for your domain of expertise, you learn to recognize what is blatant opportunism. I get that for players it might look strange, but so far he's been solid on the theme.
But to be honest, as good as you can be on the video games theme, that will never be enough to make me vote for you, and I'm pretty sure I'm not the only one.