Because atheism is a natural result of high education, critical thinking, scientific knowledge and other things that socially are discouraged for women by our institutions - Gender roles for women put them in a position where being religious is perfectly compatible and even recommended - The concepts of purity, virginity and obedience come to mind - For men there is greater freedom and possibility to not believe, and it makes more sense. This isn't biological, it's merely a result of social constraints, as it is possible for women to be atheist.
Whoever fights monsters should see to it that in the process he does not become a monster. And if you gaze long enough into an abyss, the abyss will gaze back into you
