The main "bad actor" in this situation imo is NATO and implicitly the US. They pocked the bear and the bear bite back...

Domestically Kremlin is "selling" the war as a liberation campaign against a drug-addicted nazi regime that is performing a genocide against the Russian-speaking population, internationally Kremlin is "selling" the war as self-defense against NATO expansion. I don't believe an inch in the latter explanation, I think Putin would have invaded no matter what kind of concessions "the west" would have given before the war. This war was started by Kremlin alone, without any provocations from NATO nor Zelensky.

Currently there seems to be sort of a proxy war going on, with "the west" sending military hardware over to let the Ukrainians fight the Russian military on Ukrainian soil. My impression is that this was not at all an intended plan of anyone. "Everybody" (and certainly Putin) was expecting Kiev to be overrun within some few days, and all of Ukraine occupied within a reasonable time. In this scenario there wouldn't be any need for sending weapons over to Ukraine, because they would not be able to utilize it. Surprise, surprise, the Ukrainians strongly want to keep their democracy and wants to become a member of the EU, not a Russian puppet state, and they are willing and able to fight back.