How a power can blunder and still win

Can a country commit a major blunder and still win the war?

Yes; material depth can absorb errors, and an opponent may respond badly to an unexpected move.

Victory does not prove that every decision was sound. A stronger economy and logistics system can let a belligerent absorb mistakes that would ruin a materially weaker opponent. An irrational or unexpected move can also provoke an even worse enemy response because it falls outside the opponent's planning assumptions. The outcome may therefore favor the side that blundered without turning the original decision into good strategy.