Women have always been involved in combat, beyond just support roles, and at all levels. I have seen female historical wargamers. DOM has a history degree (she got it at the same time as her EE degree), we she focused on military history (WWI). I have female colleagues who are senior commanders in modern militaries.
All that said, the male/female ratio is skewed heavily toward the male, even in contemporary forces. At the senior commander level, it is even more heavily skewed toward the male side.
The idea that any population demographic (even one from a self-selected population) should mirror that demographic in a different selected (self-selected or otherwise) population is fallacious. However, you also don't ignore the heavy influence of source populations on a selected population.
So the low proportions are neither an indication of the inappropriateness of women for this forum, nor are they surprising.
If you want to address the issue (not "fix the problem"), you need to first address the reasons for the differences between the populations. Several of these issues are identified above:
– Wargaming is a niche hobby. When you talk about very low percentages of the population in general, you can't expect proportionality.
– The number of women in combat roles, especially senior commander combat roles is much lower than the number of males.
We may not have discussed:
– There are different social pressures on men and woman – and boys and girls – in society,
– Younger people have different "fitting in" dynamics in groups than older people.
– There are a lot of former military people in wargming. That professional background also creates some "cliquishness" (not necessarily intentional) that interacts with the social and personal dynamics.
Lots of other considerations, too …