I think women are on their best behavior towards their husbands right up until they have kids. Now they got a small version of their husbands running around sans the husband's flaws, to be raised into whatever sort of man she wants/ her ideal man who treats her like a queen and will always be there for her. She no longer needs the husband for his seed,
and child support and alimony means she can completely cut the husband out of the child's life and raise the child without any dissenting points of view from her own. I truly think motherhood is the turning point for a lot of these women, because the fear of dying alone/ the desperation has been removed from the equation, so her true colors can emerge.
Just my observations