For stay-at-home spouses, who are still overwhelmingly female, housework tends to alternate between physical activity and rest breaks. These rest breaks are necessary because housework is more strenuous than sitting in an office. They're also possible because there's no need to put up a front of constant productivity like in a work environment. Finally, they're frequently alone. All of which makes short games you can dive into for five minutes at a time perfect for this kind of work pattern.
Again, pretty well documented. But I think that outside the work day, there are more interruptions for women. People feel entitled to womens' time, asking them to do chores and errands, assuming they're emotionally available. It's much easier for a man to say to his family or friends "I'm going to spend three solid hours on my hobby, please don't interrupt me".
So there's plenty of women who have zero problem with a bit of violence in their gaming, who enjoy complex games, and who don't need a "dumbed-down" experience - but the way that their time is structured means that casual gaming is much more feasible.
It's an explanation that definitely feels truthy, but I wonder if it's possible to get some hard data to substantiate it.