@Sviatogor So what you are saying is those people speak Russian, but they declare themselves as non-Russians? Or if they declare themselves as Russians are they even aware their origins are non-Slavic?

But I completely understand what you mean. Russia was an empire and it resettled some of its population as there was the need. Soviet Union wanted to maintain hegemony in those areas. It was similar like in Austro-Hungarian empire. Sizable German population remained in Serbia and Romania after dissolution of the AH empire, so similar faith followed the people like in the regions you mentioned.