[overpaidgoogler]

I would not read to much into it. This is a very specialized competition that selected 6 people from an entire country.

Some aspects of soviet education are very conducive to these competitions (e.g. an emphasis on euclidean geometry). Because of this, a top 10% student from a former Soviet country will do much better than a top 10% American if neither have extra training in this sort of competition.

If anyone is interested in discussing women in STEM in general, this article is a very poor place to do it. Eg the US has done extremely poorly up till now compared with similar English speaking country's. There are just so many idiosyncratic features at play.