The story i've heard is that the olden days, operating a computer was seen as clerical work, just like being a secretary, so ideally suited to women.
Then we got 8-bit microcomputers in every home, and operating a computer became a technical hobby, so ideally suited to boys.
The generation of boys growing up playing with computers, and girls not playing with computers, swamped any existing biases in the industry.
I wonder if the communist countries had the former phase, but because not so many homes had computers, not the latter.