Why is this a surprise?
There is a reason why this is true, and I have been saying this for years while most "experts" appear puzzled about it. The reason the pay and prestige declines have nothing to do with women's skills, education, or perceived lifestyles of dropping out of the labor force to take care of kids/parents. It is because of the concepts of the family wage and primary and secondary employment. Anybody who researches this at all knows this is true.
It is the belief that since all women are married or will get married, they don't need the money the way men do because women are supported by husbands. Employers denigrate women's employment in traditionally female jobs as well as within male-dominated occupations because they believe these women are supported by men. They feel they can underpay women in good conscience. Of course this has nothing to do with reality: women who dare live independently of men are screwed every which way economically and face old age in destitution; never-married women fare the worst of all because they have to do it all without the buffer of a second income and aren't eligible for SS spousal or survivor benefits. They typically are not homeowners or are beneficiaries of life insurance policies, benefits married women more often than not have.
The "family wage" concept, pushed by labor unions after the second World War, said that since men support families, they should make enough money they can do so. These "family wage" jobs, which had little to do with skill or education, were reserved for men. These jobs were considered primary wage or primary earner jobs. Women, it was seen, worked for extras, so they were secondary earners making secondary wages. THIS concept underlies ALL sex discrimination against women in the workplace. It has no basis in the reality of women's lives, but women as a group pay a terrible economic price for this concept. It ain't rocket science, folks.