Putin believes the collapse of the USSR was a big mistake, he doesn't view Ukraine as a real country, and probably not any other former soviet republics either.
We know for sure though, that all of Ukraine and then Moldova, was his plan.
Listen, we aren't talking about a full-scale invasion of western Europe, they aren't going to invade Germany or France, but they will for sure try to cause instability in the "lesser" member states in the east, pick apart the baltics, piece by piece.
He describes the fall of the Soviet Union as
"the greatest geopolitical catastrophe of the 20th century", which is true in a sense, because it gifted the US a free pass to rule over the world without any kind of push back. Given the human nature, it's never good to have a country, or anyone for that matter, with that much power without counter-weight because it always ends in tears. Putin also said "
Whoever does not miss the Soviet Union has no heart. Whoever wants it back has no brain." Now we can debate the truth and intent behind this statement, but at least quote him properly.
He views the constant expansion of NATO to the East since 1991 as a threat to Russia's security. From a Russian point of view, that's not an outlandish analysis. Ukraine being part of NATO is for strategic and military reasons a big no-no for Russia, just like the US would never allow Russian or Chinese military bases on Mexican soil. That is the crux of the matter and I believe that Russia will never compromise on this point, at least not under Putin. Just to be clear, I'm not justifying the invasion of Ukraine which is fundamentally wrong. Just trying to understand Russia's motives and course of action, without giving into the laughable
"Evil Russian Sauron trying to conquer and destroy the bestest civilization ever" horseshit.
No, we don't. Let's for a second abandon all logic, and say that Russia successfully manages to conquer a country as big as Ukraine with just 300,000 soldiers. By what kind of miracle would Putin be able to keep it? Do you know how difficult (and costly) it is to occupy a country which population doesn't want you there? Do you understand what it means in terms of money, manpower and military actions? History has already answered that question for us: it's impossible. You either force them out or kill them all. Or most likely, you just leave at some point. Now if you're talking about a regime change that would act more in line with Moscow's interests, that's another story.
Causing instability for countries that don't play along, as wicked as it is, has been part of geopolitics for millenia. Every single country did and still does it, the West in particular with great success and a quite astonishing number of victims around the world. And it's not going to change. People in the West are crying foul right now because they're on the receiving end for the first time in a long while.
The Baltic states are all EU and NATO members, and their populations really not fond of Russia. The latter's attempt to destabilize them during the current war, using energy as a weapon (the only one it realistically has), not only didn't work but also sped up their process to shift away from Russia as main energy supplier. All in all, it's been bad business for Putin. So what kind of trouble can Russia possibly cause, aside from nuking them?