Clearly larger companies are likely to attract more risk averse candidates but they also typically offer better health benefits, better work/life balance, and are more likely to have an hr department that can maybe mitigate some of the worst sexism that crops up in our industry.

There's also probably a bit of a gravity affect happening. My entire career I've never been on a team with even a single other woman and it would certainly be a nice thing to go somewhere where that wasn't the case, so maybe it's just easier for companies that employee women to hire more women.