Some quick research on this suggests that the average college graduate in engineering (which is programmer material, at least programmer material for companies like Google) is around 130. Sources like [0].

Therefore it is not unreasonable to deduce that people who work as programmers in prestige companies are, on the average, from the very right-hand tail ends of the normal distribution curve, and the differences of men and women (on the average, again) are significant enough to cause an over-representation of men among this group.

The same thing that causes an over-representation of men among homeless alcoholics at the left-hand-side end of the normal distribution.

[0] https://qz.com/334926/your-college-major-is-a-pretty-good-in...