Putin believes in that. I don't think the Russian populace does.
You'd be surprised at how much nationalism and ethnicity plays a role in EE.
Even the Ukranians are on camera willing to die "for their country".
Look at Djokovic ... his issues with Australia were seen as being a repudiation for Serbia itself. Serbian president said "Joker is serbia and serbia is Joker".
I have spent time over in EE and it is stunning the degree to which nationalism plays a role in people's motivation. Probably because they don't have much, they need an ego bolstering -ism to cling to. And then when you attack the things associated with that -ism (in word or deed) the "-ism" holders feel themselves attacked.
So there romantic yarns about "greater days" before some "great betrayal" find fertile ground in the minds of many in that part of the world.