This is an extremely delicate subject - it should be our goal for everyone to feel welcome in Lemmy and seeing a low sample of cis women on the platform might indicate that women are feeling unwelcome here. That tracks with general experience of mixed gender internet spaces where women will experience increased harrassment (and might actually poison a survey since one defensive reaction is to just deny that you’re a woman).
This is slightly complicated by the fact that we’re not drawing from the general human population, Lemmy’s user base trends strongly to the technically literate (which is a gender biased population for terrible reasons outside of Lemmy specifically) which may account for part of the result. The result may also be impacted by the fact that technical fields have traditionally been more accepting (not fully accepting or anything - but less awful) when it comes to LGBT+ folks - so we’re likely going to see a higher than normal presence of trans folks as a result.
Additionally, Lemmy is a style of forum that is extremely similar to Reddit and so it’s likely that people who had negative experiences over there are extremely hesitant to try Lemmy - Reddit is quite infamous for hosting openly misogynistic community, promoting misogynistic views, spawning IRL misogynistic movements and allowing a lot of toxicity in DMs towards women in particular. It’s likely that Reddit has just burned a lot of women off ever considering a forum like thus.
Lastly, I’d hope we can avoid specifically trying to increase one demographics engagement on the platform, I think there’s a distinction between making sure everyone feels welcome and trying to attract a specific demographic - while that distinction may not feel significant to some people it, at least, makes the difference between being good and being cringey to me.