I suspect this is driven by women's culturally-conditioned lower belief in their own ability, as well as men's conditioning to believe they must go to college.

The women who would fail have already self-selected themselves out of CS due to believing they won't be able to hack it. Therefore women who actually do start a CS program are likely to be the most driven ones with the greatest likelihood of success.

Whereas men are conditioned to have more belief in their own ability and to see college as non-optional, so they're more likely to commit to a CS degree (or any college degree) without realizing they won't be successful at it.