Computer programming once had much better gender balance than it does today. What went wrong?

[SatchelSF]

I found this ironic in the article, regarding the very first successful woman they profiled:

But even as Wilkes established herself as a programmer, she still craved a life as a lawyer. “I also really finally got to the point where I said, ‘I don’t think I want to do this for the rest of my life,’ ” she says. Computers were intellectually stimulating but socially isolating.

Could it just be as simple as males on average prefer working with things and females on average prefer working with people?