Yup, my understanding is there is a lot of oil in Ukraine (I think donbas specifically but don't quote me on that). And arguably more importantly, a major pipeline runs through Ukraine. My understanding is the EU is currently very reliant on Russian oil and they would very much like to not be. Hence, why Ukrainian membership to NATO is so attractive.

I think a lot of people in the West dismiss Putin as a nutjob, but I think there is a rational reason for controlling Ukraine. Oil is Russia's largest export after all.

All of that isn't meant to excuse Russia; it's unethical to murder for oil. But it's intellectually lazy to dismiss a rational actor (albeit an unethical actor) as crazy. But capitalism gonna capitalism. And until we put an end to capitalism, people are going to continue to murder for money.

Eastern Ukraine has a lot of natural gas, actually. Plus Ukraine has a lot of pipelines for getting that natural gas into the rest of Europe. Technically not oil, but one of the main objectives of the war was absolutely about controlling Europe's access to fossil fuels.