I don't know why that war is being fought, but for example the scenario "if Ukraine joins Nato, then further fighting in the Donbass or the Crimea would lead to war with Nato, so those territories would be lost" seems at least possible. And if Russians were murdered in the Donbass, even "we want to defend Russians in the Ukraine" could be a possible motive.
The theory of "genozide on Ukrainians" sounds very implausible to me, given that there are several possible real motives for the war.
Mind you, I am not saying it is justified, I don't know enough about it. Personally I would guess more is going on than just "Ukraine becoming Democratic is a threat" or "Putin has become crazy".
