Revolut founders are from CIS countries (Russia and Ukraine). It quite common for high-school graduates from post-Soviet countries to participate in STEM Olympics as the medal can open the doors to best tech schools without entrance exam.

It not so hard as it sounds. I get the two medals on Physics when I was in school, so did plenty of my classmates.

I guess by that time they were targeting mainly CIS developers as they have and R&D in Moscow.