Why this remind me or 1990s breakup of Yugoslaiva
Partly.
The Serbs of the Krajina seem to share some similarities with the Russians of the Ukraine.
So do both with the Sudeten Germans, or a lot of the Austrians during the Anschluss.
More like the 1930’s I think. In the Crimea a Russian takeover cannot be opposed because there is a very limited anti-Russian population and the territory is extremely discrete and well defined. Geography is everything.
In the Sudetenland the Germans seized the defensible terrain around Bohemia, and I believe you will soon hear that the Russians have seized Perekop.