I think it’s just that everyone plays games to some extent. I don’t think any of them are thinking they’re reaching “gamers”, just they realise it’s a platform they can get their message out on. I don’t see this being much more different than handing out flyers at a farmers market out outside a stadium/movie house, etc.
When you consider 400k+ people tuned into that stream. How difficult would it be to normally get that kind of attention? Or consider how bernie used all the various streaming platformers during his campaign. They’re just lowering the barrier to informing people.
I also think a key part of what makes this all successful is it’s honest. They’re treating the audience with respect. They’re not pretending to be pro gamers, or saying stuff like pokemon go to the polls, thinking they’ve just said something very smart. For comparison check out what Biden was doing in Animal Crossing. Talk about embarrassing!