It’s worth mentioning, that although the Russian (and former Soviet) army is large, is has never been, what one would call, a great army. Yes, they are ruthless and brutal, but the army is mostly made up of conscripts with very low morale.
Their history of losses outweigh their victories, and most of the losses are to smaller countries. Chechnya, Poland, Japan, Crimean War, and Sweden and Finland fought Russia to a standstill. And then Afghanistan, everyone’s loser. WWII, Russia would be Germany now except for Allied troops on the western front. Of course, the west might also be Germany without the Russian on the east.
Point being, the Russian offensive shouldn’t be surprising and is not a foregone conclusion of victory. But Putin is a brutal KGB bastard who will certainly not spare a life to get what he wants.