Evil tends to have, and sometimes use, the advantage of surprise and reluctance to acknowledge evil. Hitler might have been setback by France and Britain when he re-occupied the Rhineland at a far less prepared stage in his rearmament. Despite all Japan did in China (for years!), the attack on Pearl Harbor was a successful surprise. Stalin’s blockade of Berlin was broken, not by vigilant preparedness, but by sheer determination. Kim il Sung’s invasion of SoKo came within a few scores of square miles of over-running SoKo.
The Bulge was a last ditch effort to give the allies a severe setback and so prolong the war in the West as to discourage the allies into a negotiated peace. Whether it could have succeeded is an interesting question. I doubt it, because the determination and initiative that stopped the German offensive and turned it back would have been there even had the Wehrmacht advanced another 100 or 200 miles. The lesson that should have been learned - but wasn’t or has been forgotten - is that complacency in high places is usually quite costly to those in lower places.