No one is prepared for war or likes to be invaded but you also don't get orchestrate a war and not have adequate resources to finish that said war.
We only see the beginning of a war but the finishing end is unpredictable, i think Russia overrated itself right from the beginning and what it expected wasn't what the actual situation is.
In the case of Putin, his invasion to Ukraine has lasted for six months and according to reports gotten from professors studying the war, it was gathered that Putin felt the war would last for a week or so and then Ukraine would give in, but I guess he had another thing coming.
Later in live i believe Putin will regret some of his present actions on humanity because innocent bloods will definitely count, fight and speak for themselves, he that lives by the sword will always die by the sword, there's no doubt about this because its a proverb from the wise.
But then there's the case of replenishment of soldiers because should a war last this long, there's bound to be loss of both manpower and weapons.
Ukraine has alot of backing up powers, what has Russia got as backup?