But they DON'T need buffer states. They say they do, but NATO has not invaded anyone. Others have begged to join NATO and to join the EU and free world/free economy, but there is no imminent invasion except by Russia against anyone it thinks it can bully.
And without Crimea they still have access to warm water ports on the Black Sea as they have other territory that is on the Black Sea.
The real problem is that they are aggy, and have the little brother, red headed step child, small man syndromes where they want everyone to think and treat them like they are the greatest at everything and bow down to them. Meduza had an article where they got quotes from Russians who did not and don't support the Ukranian war, but then say... "But now that we are in the war we HAVE TO WIN", even as they say how horrible what they are doing is.
I am sure not everyone thinks this way, but it is somewhat of an ingrained Russian cultural perspective.
https://meduza.io/en/feature/2023/06/03/the-only-thing-worse-than-war-is-losing-one?utm_source=email&utm_medium=briefly&utm_campaign=2023-06-06