First, I don't know; I'm simply guessing.Most of these women give multiple reasons. It appears to be what might be called the perfect storm. Relevant issues are: unequal treatment of men and women, LGBT exclusion, personal trauma, scandals, simply losing faith, other things in life taking priority, rigid gender roles, teachings on sexuality, too political, and hypocrisy of the leadership.
Second, the Abrahamic churches have all tended to emphasize intolerance of homosexuality let alone present day gender roles, and stress the centrality of marriage, roles for the male and roles for the female in marriage, the words of God putting males in charge. There are exceptions to all of these, of course, but they're not the mainstream by any means.
I'm reminded of the old joke about marriage ─ marriage is an institution, but who wants to live in an institution?
Go, gals ─ and boys ─ and find your way as you honestly wish.