He was young and stupid, and, because he was stupid, he had no doubts.
When she suggested that she'd like to become a doctor, maybe even a medical researcher, he smiled down at her, full of love and condescension, and told her that women were not made for that sort of thing. Women were too delicate and not intellectually capable of the effort required. He was very sure of what he said. She was full of doubt, and accepted his clear conviction of his own rightness.
It was that sort of culture.
Over the next fifteen years she came to understand (without a doubt) that he really was stupid. And realised she'd wasted her life because of him.