"You have a megalomaniac dictator waging an unnecessary imperialist war of aggression ."
Yes, one that was raised by the KGB, and his work possible consisting of coordinating left wing terrorists in the west.
"That should make it pretty straightforward, no?"
Sadly no. Because his character and the general political ideas and red lines of the russian establishment were known.
Ukraine was russias sphere of interest/domain.
So the west going into ukraine, helping with the coup and promising them EU and NATO, while knowing that russia can never accept it - was a clear path to war from the beginning.
Would the US tolerate mexico become a china military ally? Doubtful. One of the unwritten laws.
The geopolitical realities are, that it was known that going into ukraine would likely lead to some war.
Which is why most of the world considers this war a proxy war between Nato russia. And it partly is.
But yes, it is also a war for independence of a small nation against an evil empire. But the empires in the west seldom care about the actual people on the grounds. They care for their interests. And currently ukraines and Natos interests are mostly aligned, which is why they get support.
If china suddenly becomes a bigger problem and now there would be a need to play Putin against them - then Ukraine would be on their own very quickly.
It is already starting now, with the west medias more and more implying that it was indeed Ukraine that blow up north stream. Whether they did it, or not: this is a way of showing them, they can change the narrative in the west quite quickly. War is dirty. And also Ukraine has lots of dirt on their hands now. Showing some of that dirt will make the public change opinion. This is geopolitics in action.