Now, there is exactly zero appetite anywhere in NATO for invading Russia. But Putin doesn't understand that - doesn't understand that, when the leaders have to answer to the voters in elections that they could lose, the leaders have to be very wary of body counts. So Putin is terrified of a fantasy, but his terror is still at least somewhat real. It's not all bullying.
It is.
>launched their invasion
You are reproducing Russian propaganda planted all over the English speaking internet. About Russia's desire to secure itself through buffer zones, when in reality it's just plain old imperialism.
Geographical buffer zones and natural borders like mountains are mostly irrelevant for modern air-superiority dominated warfare. It's not 1940s anymore. US expeditionary force is delivered by the sea. An attack could already be launched from the Baltic states, since about 2004. And Putin perfectly knows that nobody would attack a state that has the highest number nuclear warheads in the world.
Ascribing some level of care for Russian interests and security to someone like Putin is the height of naivete. Putin will leave Russia much much weaker and thus less secure after his death, than the 99 other timelines, where it isn't ruled by an egotistical wannabe tsar. He only cares about himself, his family and his friends, and that's it.
If he truly cared about Russian future he wouldn't have started the current conflict with Ukraine that's been going on since 2014, because the economic losses from that over 2-3 decades are tremendous. A difference in 2-3 percentage points of GDP growth results in several times the economy size of losses. And further escalation would cripple the economy even more.
Or are you saying that it's propaganda the Putin is worrying about that? I've never heard them say so, so I don't think it's a common theme of their propaganda.
The propaganda insists that that kind of thinking is still relevant in 2022 and that Russian elite truly believes that, and not using it as an excuse for imperialistic/revanchist expansion.