I’m not entirely sure this is true. Women are frequently also sexist against other women because we’re used to traditionally seeing men in power. And the men in power make sure that they and other men stay in power — such as by supporting each other with ad campaigns, making sure they get the best jobs and appear to be the most qualified candidates, etc. It’s not just about the number of voters. We don’t see a proportionate number of queer or BIPOC legislators/politicians either.