In their military planning they often demonstrated tactical brilliance coupled with unbelievable strategic ineptness. Many of their military campaigns failed after initial successes because they simply failed to follow through and properly exploit their early victories. Very often they would easily overrun their opposition and suddenly find themselves without the logistics or coordination to consolidate their victory.

Perhaps the most obvious examples were in their advanced weapons engineering. Their V-weapons were invincible, but cost more to produce than they inflicted in damage on their targets. Every time they hit London or Antwerp with a V-2 it cost them more money to build and launch the missile than it did for the Allies to repair the damage. Their other technical achievements in jet aircraft, high performance submarines, and other advanced weapons technology were technically superb, but never were applied wisely to their war effort. Their armor's performance was second to none, but its complexity and maintenance demands eventually led them to succumb even to inferior Allied tanks. Sometimes serviceable, dependable quantity is better than state of the art quality and perfection. It's certainly more cost-effective. Even their radar technology, in many ways superior to the English, was never fully integrated into their air defense system the way the Brits did. They had great gear, but lousy organization. And on the economic front, their vaunted Teutonic efficiency and science could not keep up with American industrial management techniques. We didn't just have a bigger economy, we had a better one.

I think their problem was their strict, narcissistic ideology. As long as you are convinced you are intrinsically superior to your opponents, you will never learn from your mistakes, or their successes.