Some of the above is bullshit.
Historically, as in over the past 100 years, there were periods when women were more encouraged to go into computer and periods where men were.
You have the obvious documented big names in early computing. I couldn't find any historical statistics before the late 60s though.
In the late 60s to 70s you get a rather wide range of (guesses?) that from 20% to 50% of IT workers were women.
There were popular magazine articles that featured the female programmer (though they seem pretty sexist, it still shows that women in computing was probably a social norm).
In the 80s something like 40% of IT workers were women (I see various statistics on this, from 37% of comp sci degrees in 1984 to 42% of developers in 1987).
It's only in the last 20 years that there has been this huge drop.
More women get bachelor's AND master's degrees than men, they're just going elsewhere and honestly that should be fine with society because that indicates to me that it's mostly a matter of personal choice.