Hardcore gamer = someone who plays only cinematic grizzed white dude games and/or military fetishizing FPS
Casual gamer = anyone that is not a 15-25 yo male, and/or plays anything outside of the previously mentioned games, especially if those games are colorful.
So basically the gaming community is full of gatekeeping, misogyny, toxic masculinity and general chuddery. They make sure they're the loudest voice heard when anything about games is talked about, and won't be happy until all games a homogenous stream of bland, hyper-realistic but with a grey filter slog of mindless action with no heart or soul. And don't you dare force them to read any dialogue or story.
AFAIK the arcade boom was pretty popular with both men and women, since at that time it was a social hobby and kids were doing a lot of hanging out and hooking up at arcades. It wasn't until the turn to console gaming, which was primarily an anti-social activity, that video game advertisements started really focusing in on young boys. Nintendo bears a lot of the blame here, since they defined the western market following the big crash, and they saw the NES as exclusively a boys' toy - but it wasn't just them of course, in particular I remember the OG XBox's marketing doing a lot to create a "bro culture", along with stuff like the channel G4, which I think was created intentionally as a reaction to the previously existing perception of gamers being nerdy.
Children (overwhelmingly boys) who played vidya games were nerdy. There was a brief period during the Pac-Man era when vidya games were for everyone, and soon it went into hardcore weirdness. Games got hard and unless you had the patience to play again, and again, and again, and again...you can forget being a part of the crowd. Games with 45 levels when nobody ever got past level 4.
So there's a bit more to this, if I remember all this correctly, Nintendo couldn't exactly call the NES a 'video game console' when they started selling it in the US because the crash had pretty much made that a really bad financial move to call it as such. And also they had to sell it in the toys section to start with, which has had and still has a lot of segregation between boys and girls toys. And also considering how brick and mortar stores have acted for a long time, they likely had a bit of a hand in this in the way of demanding nintendo to pick if it was a boys toy or a girls toy or else they won't stock it.