JetBrains is actually from Czech Republic, not Russia. Yes, they have offices in Moscow and SPB, but also in Munich and Boston - that does not make them German or US company either.
I think the owner decided to register the firm in Czech Republic because it is more western and also a country with Slavic language. As far as I know both the owner and majority of developers are from Russia.
You are right, I had a look into business register and names of owners like Sergey and Valentin are not exactly Czech names.