The long length attests to the eventual victory of the defender, not the attacker. Russia leadership thought they could win in days, not years. They’ve had 30,000+ hours and haven’t captured Kiev yet, assuming it’s a lost cause from day 1 is completely unjustified. What reason do you have to believe it was decided from day one?

How much of history do you have to ignore to think a country in a defensive war cannot hold off against a larger army until attrition causes the attacker to withdraw?