I think it was seen as a success since it was the event that turned the war around and led to the eventual victory of the Allies. Sort of a vacuously true type

I think it was seen as a success since it was the event that turned the war around and led to the eventual victory of the Allies. Sort of a vacuously true type of success, the operation might have failed to meet most of it's objectives (I don't actually know) but that doesn't really matter since it led to "winning" the war. However, of course, the truism that there are no winners in war remains. No military operation is going to have a low cost of human life, even a successful one.