The prime motivation for Russian foreign policy, including this war, is regime survival. They effectively put other domestic policy into a coma, and turn foreign policy into domestic policy. Ruskie Mir, WW2 death cult, FSB active measures, insane school curriculum, etc. This approach was largely caused by the counter reaction to the 2012 protests in Moscow about Putin’s reelection, which he views as a CIA plot (even though the US had pivoted to China and Russia was in the G8.) For some reason, Putin and his group simply refuse to believe ordinary Russians wanted agency and think for themselves (hat tip to Stinky re: illiberal point.)
Anyway, it worked brilliantly in 2014 and somewhat in 2016. The problem is that it’s a like a drug, they need to amp up the dose as time goes on or circumstances change. So with the collapse in oil prices (2015), a poor economy and the bungled response to COVID, the regime was feeling vulnerable, especially since there is no path for an orderly succession. Putin fears the Gaddafi solution, and the New Russian Nobility, a merger of ex KGB and organized crime has a lot to lose if reform comes to Russia (or more likely, IMO, another group of gangsters take over.)
So this is the result. War with the west, the regime needs to do this to survive. It extends beyond Ukraine. It has to to be effective. The regime fully intends to challenge Article 5 and smash the EU. They want Russians to be perpetually engaged on war, foreign enemies, etc. etc. but never on their own domestic situation.
So, I can give Count benefit of the doubt and wave away MAGA talking points as a matter of convenience. But to suggest this is simply Russia-Ukraine and why risk this going WMD (though a smashed dam is WMD) is plainly wishful thinking. It has come to this because the Russian regime wants it.