The same question is asked by engineering and physics departments in universities, people seeking to diversify air traffic controllers, and a number of other areas. My wife did her PhD dissertation on a closely related topic.
As a population, women are simply less interested in certain fields (and as a population, men are less interested in some other fields). Much of it originates in biology (brain wiring). Organizations jump through hoops to attract under-represented groups, including women, by trying to modify the field to make it more "interesting" for those people, but it doesn't work.
Focusing on women, many are encouraged through various incentives to get into fields like engineering and other fields as mentioned above. High percentages drop out because they find that it isn't interesting for them and they don't do well in it. If they complete the program, only a small percentage work in the field in a "technical capacity". They tend to switch to other occupations or move into administrative/management functions.
Unfortunately, this is all very politically incorrect. It's virtually impossible to even research this anymore because it runs counter to the meme and agenda in academia, the government agencies that push this type of social engineering, and employers who are pressured to fall into line. This question is an indication of how endemic the narrative has become without being challenged.
But the bottom line is that there are certain things that relatively few women are interested in relative to the percentage of men interested in it.
The same applies here. It isn't a hostile environment; we aren't discouraging involvement by women or making women feel unwelcome. I asked my wife to read this question and share her thoughts. I would classify her as an expert (both as a woman with a science background and a researcher in this area). Her response was that relatively few women are interested in the site's subject matter, and most of the ones who are have better things to do than hang around the site and be top contributors (it's just not on their priority list).
What the HuffPost article talks about is the fact that more women are taking on DIY projects. But women do it to to get stuff done. They don't do it because they like playing with power tools, and they don't invent projects just so they can use their power tools, or to procrastinate doing stuff they need to do but isn't as fun. They fit it into their other responsibilities. So the fact that women are doing a lot of DIY projects has no bearing on their desire to invest time on the site being a serious contributor. And nothing we do to alter the site experience will affect that.
This answer was intended only as a summary explanation, but the lack of references has been challenged. This is a broad field of study, but if anyone is interested in delving into it, here are some places to start:
Differences in "brain wiring" are measured by tests for interest, aptitude, and personality characteristics. People who do well in, and enjoy, fields like engineering score highly on measures of "mechanical reasoning", things like spacial visualization ability as measured by mental rotation tasks and the like (on average, men score one standard deviation higher than women, which correlates with why so many more men are attracted to, do well in, and enjoy these fields than women).
There are other measures that correlate highly with the abstract sciences, like "theoretical thinking". Some of the characteristics are measured by tests of ability, some are personality assessment tools, some are personality assessment tools where the results are compared to the profiles of people who report enjoying their occupations in different fields or are successful in different fields.
Analysis is done on huge statistical databases that are compiled from various tests, such as ASVAB, NLSY, Stufy of Values, The Strong Interest Inventory, and numerous others.
If you Google "sex differences in interests" or "gender differences in interests", you will find endless reading. But a few specific places to start: "Biology at Work; Rethinking Sexual Equality" by Kingsley R. Browne, Rutgers University Press, "Sex and Cognition" by Doreen Kimura, The MIT Press, "Gender and Fair Assessment" by Warren W. Willingham and Nancy S. Cole (Educational Testing Service), or pick from the research of Dr. Richard Lippa (CSU Fullerton, et. al.)