The former "Soviet Union" & Comme-conn collapsed in 1991.
We made a side agreement that "NATO" wont expand eastward in return we offered closer relations & economic ties with the "West".
Since then NATO has only "Expanded" and Belarus & Ukraine are litterally their backyard and Moscow aint having it.
Europe wants to push thru but doesnt have the military resources .
America does but this could also become a nuclear exchange between Russia and The West.
Culturally Ukraine much more like many Eastern Soviet Republics.