Because evil 👿

Putin watched the Thanos movie and wants Ukraine's infinity grains.

Putin is Sauron. Well, they use more words, but they means literally this. Also their view on the war is much much worse than the canon War of the Ring, which was actually pretty plausible when you count the numbers of combatants while libs are just on the level of "Sauron send uncounted orc hordes and didn't care how many of them died"

It's obviously because Putin is an evil dictator and he did it because he loves killing poor wittle nazis in Ukraine.