Russian isn't just spoken within Russia, of course, but across many parts of the former USSR as a first and second language, and by a major Diaspora. A significant number learnt Russian during the Cold War in central and eastern Europe, and even Mongolia.

It doesn't have the prestige it once had, for reasons we know very well, but it is still a significant language, and one of the main official languages of the UN.

The Vatican has expressed interest in the region for some time and has tried to broker ecumenical deals with the Russian Orthodox Church not just missionary efforts. So yes, I am surprised not to see it there.

Yes, I agree about Korean. I could think of some other languages in Africa and Asia.

Most Arabic and Chinese speakers are not Catholic either.

The Vatican has shown a persistent interest in Russia, and yes, there is a significant Russian speaking Catholic minority, as well as a potential convert base. If I remember rightly, Russia (or the USSR) gets a prominent mention in the Fatima narrative.

Russian has declined a lot in importance over the past thirty years, but it is still a major world language in terms of its spread. It is a surprising omission.