It's both. Women were definitely excluded, especially in the 80s and 90s. Ads were a little....let's say a little focused on the male gaze: https://www.reddit.com/r/gaming/comments/1k3dre/game_boy_poc...

Games went very hard into the "shoot stuff" genre from get get-go (presumably in part because it's comparatively easy to design and make) and stayed there, and that's also a factor.

But ALSO, yes, the folks making games tended to be male, and so the target audience also tended to be male.

But on the other hand, as more games became available, and especially as mobile gaming on phones became possible, women quickly climbed back up to being about half of the gamers, so it was certainly never about any inherent differences in how much they'd like games so much as just what sort of games different people might like.