Malorossiya, literally "Little Russia", gained independence from the failing Russian Empire during the 20s. Since around 40% of the Ukranian population of Malorossiya left for Green Ukraine, the country was populated by more and more Russians and White Ruthenians, causing Malorossiya to lean more towards Russia.
basically modern Belarus in our timeline ((fun fact: Malorossiya's borders were created in MapChart, using the Victoria 3 state map.))