This is unrelated to the main thesis of the article, but worth pointing out as too many people equate the Cyrillic script with Russian language.

The Cyrillic script was invented in Bulgaria (during the First Bulgarian Empire), and was used to write Bulgarian language, creating a huge literary corpus, long before it began spreading to Kievan Rus. The Russian language itself comes from Old Bulgarian / Old Church Slavonic, as does Serbian and other "Slavic" languages.

And no, Bulgaria was never part of Russia nor the Soviet Union.