... Brilliant women who aren't interested in programming. Why not?
If they're turning away from programming because of sexism, we can and should be fixing that.
If they're turning away from programming because women are less likely to be interested in systems thinking, and thus fewer women find programming as interesting as men do then its fine. Let the women who want to program be programmers. Let the women who want to be lawyers, or mums, or doctors do that instead.
The research suggests that both of these things are happening. If you talk to girls thinking about careers they say "programming is for boys". Also, men and women have very different interest distributions. And one of the clearest ways people express their personal interests is via their career.
You could also ask the same question about a career with an inverse gender distribution like nursing. Why are only ~10% of nurses male? Some of the effect size is probably sexism, but probably a lot of it is that (statistically) fewer men are as interested in caring for other humans as women are. Any sexism found should be fixed. But if the difference is due to expressed preference, its fine and we should all chill out.