Youre better off asking why women overall are more likely to read. It follows that more women would be authors. And it gets even worse if you’re looking at book club participation where women are much more likely to participate ime as the frequent only man at book clubs.

For your fantasy book authors, you probably were expecting the opposite because society historically pushed male authors to the forefront and you can still see this today where many people will list their top fantasy books and not a single woman author can be found. This is either inadvertent or intentional sexism.