The Google memo made a number of points on why women might be less likely to pursue leadership positions. Women prefer lower stress jobs and more social-work balance. Men are more competitive than women and may have more of a natural drive to "reach the top". But the biggest effect I think is that our culture values men based on their job a lot more than women. Men have a lot more pressure to get a high status job.

Note that all of this is purely a "interests based" argument. No one is saying women would make worse leaders than men. As you mention, there might even be some good arguments that they would be better at it. I'm just saying there are good reasons why they might be less interested in pursuing that. As opposed to it all being because of sexism.