The overall analysis is very good, but the matter of Putin's motivation is still underexplained.

I get why so many people find Mearsheimer's reasoning to be correct - it really fits Russia and the wordviews of Russian ruling class (Post WWII upbringing in a totalitarian state + professional deformation of intelligence officers). However, it's limiting in the same way the whole Offensive Realism theory is. Let me try to explain. I'll use "Putin" as a substitute for "Russian government and ruling class" below.

Yes, Putin sees NATO as an existential threat, even though he understands there's no real risk of any military action coming from NATO unless provoked. Yes, Putin wants "regional hegemony" and thus wants to get to control Ukraine, probably indirectly, by almost any means.

But the war in the Ukraine only makes NATO stronger? Yes, however, the threat from NATO, as Putin sees it, is not only military, it's also cultural. Even though his actions will probably lead to Finland and Sweden, for example, to join NATO in the nearest future, those countries are already classified as "the West" so their military status is of lesser concern. Ukraine, on the other hand, has extremely strong (probably, the strongest of all other countries, Belarus being the second contender) cultural ties with Russia, this includes family ties, language, traditions of policy practice, etc.

Why does Putin care about cultural changes in neighbouring sovereign countries? This is where offensive realism falls short. The answer is internal politics. The main motivation for Putin is self-preservation. Ukraine "choosing West" is unacceptable for Putin, as if it works out even slightly net-positive for Ukraine it will be almost impossible to maintain the illusion it can't ever work in Russia.

If it's so important for Putin, why didn't he do it 8 years ago? You can take only so much risk and economic damage. Annexing Crimea was a guaranteed easy and swift operation and it didn't look like a military intervention for the Russian people, which is good for the ratings. As the consequences hit Russian economy pretty hard, it took whole last 8 years to hammer down to the population it's all "our enemy's fault". It also took 8 years to explain to the business elites "the confrontation with the West is for real, prepare".

But the economic damage? Putin's well off regardless. Prosperity of Russians is of no concern - Venezuela shows how low you can go and still keep your seat. Poor people and non-existent middle-class means less political activity, which is a bonus.

Speaking of elites, there were some rumours of a considerable dissatisfaction with the economic situation and the lack of the development momentum brewing up lately. Making all the top officials and close businesses complicit in War and some of them receiving direct losses from the sanctions leaves them no choice but to double down on supporting Putin's regime, as there's no alternative for them. This could also additionally explain the timing for the decision to break the status quo, but we have no info on this.

So, to sum up:

- No NATO in the Ukraine means you fully control the region. This is a good feeling for the paranoid character.

- War means mobilization and mutual responsibility of the elites, which is essential to maintaining the mafia state.

- Economic damage to Russia will totally obscure the poor management of the Russian economy by Putin's government and total incompatibility of the policies with economic growth for most of the citizens.

- Preventing the sovereignty of culturally close countries means Russia looks the strongest and the most successful of the bunch and this is good for the general support.

- Putin personally is a violent bully, his close company are mostly the same. You need to demonstrate the decisiveness for violence to be on top.

- Putin might be additionally stimulated by his messianic delusions of restoring USSR being the prime directive of old-school KGB officers. Although, it's impossible to know the truth here.

The only serious risk Putin took is with his own people: did he manage to dumb and oppress us all down to accept and offensive War and still maintain the required level of support? Only time will tell.

I personally despise it all. I saw the writing on the wall but couldn't believe it, a fool. Now I can only hope. Peace.