The thing is that older women are probably very conservative. For one thing, feminism came too late for them - to put it roughly, they still get nothing of its frills. I would also recognize that socialization outside family increased much in modern times, at the expense of "education" within family.

Other (falsifiable) possibility is that conservative women might live longer.

But the particular 75-25 distribution is not explainable by conservatvism of elder women alone.