This isn't exactly my theory, this is something fairly well documented that I have come across in general reading.
>men died on all sides in WWII
I'm not sure if you're aware of how far the scale of deaths in the Soviet Union exceeded any Western country - East Germany was probably close, which is an interesting correlation: were there any communist countries without major gender imbalances?
The overall number of World War II casualties in Slovenia was thus of around 7.2% of the pre-war population, which is above the Yugoslav average, and among the highest percentages in Europe.
It also probably had to do with religion. The US was heavily religious compared to the Soviet block. And religion usually puts women in their place behind men.
>men died on all sides in WWII
I'm not sure if you're aware of how far the scale of deaths in the Soviet Union exceeded any Western country - East Germany was probably close, which is an interesting correlation: were there any communist countries without major gender imbalances?