"What happened to all the talented female teachers?"

In the 1960s teaching was one of the few professional occupations considered "suitable" for women, and as a result many of the best and brightest women went into education. As other occupations opened up to women this resulted in a huge brain drain, with the average ability of teacher to drop dramatically.

I imagine the same happened in programming as well, as women has more choices open up to them they naturally moved on to other fields.