The current trend in the meta-analysis of Russia/Ukraine is to divide IR scholars and regional experts/comparativists with the former blaming NATO expansion and the latter focused more on Russia's domestic politics. A mix is one that focuses on petro-states. I just want to scream that it is not all IR scholars who line up in the blame NATO, apologize for Putin camp.
A certain group of realists like to define their paradigm and even the IR community in a particular way, but the reality is that there is much diversity in Realism and among IR scholars. The blame NATO crowd does not have a monopoly among realists as this Foreign Affairs summary clearly depicts.
As the Monkey Cage piece suggests, timing matters, and last year's events did not happen because Ukraine's NATO status suddenly changed. No, Russia's aggression began when it lost control over events in Ukraine when its favorite politician fled.
Realists of a certain stripe have a problem with this because it suggests that domestic politics matters--that who runs Ukraine matters because different people with different constituencies will govern differently. This is problematic for those who over-emphasize how determining a country's position is in the structure of international relations--great power/not great power; buffer state/whatever.
These Realists have another problem--in a nuclear world, what does the alliance status of Ukraine mean for Russian security? Even if Ukraine were to become a NATO country (which was not on the horizon given European objections), Russia would have little to fear if one defines security conventionally--as the fear of an attack. The reality of Mutual Assured Destruction would not change with Ukraine's alliance status. So, one would have to expand the notion of security, make it broadly defined, in order for Ukraine to be a threat to Russia. And that is a move that some of these Realists have long loathed.
One can be opposed to NATO expansion to Ukraine, as I have long been, and still find that Russia is entirely responsible for the events of late. Putin has plenty of agency and chose this conflict. It is, indeed, a war of choice. A key irony/contradiction in modern (and classic) realism is to view other countries as being pushed by the international system as if they are billiard balls but that the reactions of the US (and sometimes its allies) are blunted by domestic politics. If only the US too could react according to the clear imperatives of the international system, all would be ok, but politicians lie and lobbies lobby. Damn.