Russia is still smarting over losing the "empire" of annexed countries after WWII. It still has the Stans which, being oil rich, is good for Russia.
Many of those once occupied countries now have large minority Russian populations, some of those folks would like to rejoin a new and Greater Russia.
Much like if the Mexicans in Texas . New Mex. Ariz, Calif wanted to leave the US and rejoin Mexico (I'd be all for it)
This is a never ending song, as population shift.
Frankly, I'd be happy if New England, NY, joined the Maritimes in a new Eastern Canada, but hey, that is my great dislike of the trumpets speaking.
As an aside, Trumpy says Germany is under Russia's thumb cause they buy oil from them: So is the US under the thumb of the Saudis for the same reason?