@MangyInseam
There has been a fair bit of analysis about this. Women going into what we think of as masculine professions like engineering correlates with the degree to which the society is egalitarian. The less egalitarian the society, the more women who do get an education and enter a profession are likely to enter into male dominated professions. Whereas as the society becomes more egalitarian and values men and women, and their work, more equally, they are more likely women are to choose more people oriented types of careers.
I know the study you are most likely referring to (this one, with these corrections). But are you aware that a response to that article argues that their findings are not robust, but depend on the way the measure women's presence in STEM fields and the gender equality index they chose?
This is the response to the study by Richardson and others which points out that the Stoat and Geary results are affected by the measure they chose for gender equality and also the new measure they created for measuring women's presence in STEM fields (which is really a weird one, to be honest).
You can read the summary of the latter critic here. It argues that the inverse correlation between women in STEM fields and country-level gender equality measures are not robust to the way these two variables are defined.
In particular, Stoat and Geary created a new (and somewhat odd) measure to reflect women's presence in STEM fields and used that with one of the measures of gender equality that are available.
When Richardson and others used the more normal measure of women's presence in STEM fields (percentage of female graduates among all tertiary level STEM graduates) and the other gender equality measure (developed by Stoat and Geary, incidentally), they found no correlation between a country's level of gender equality and the presence of women in STEM fields (see Section 4 here).
Richardson and others also point out that making assumptions about individual choices with aggregate data can lead us to the ecological fallacy.
So I don't think this particular study can be used as the foundation for what you state here:
It's really difficult to see why women making choices about career preferences wouldn't be a very strong contender for the most likely explanation for all of this.
What we often describe as preferences at, say, eighteen have already been influenced by societal messages of all kinds (and, in particular, attitudes about which jobs are gendered male), so it's not quite correct to interpret someone's choices of occupation at that point as solely driven by interests which are somehow innate. Here this article matters.