Hitler had many flaws. He failed to see the value in a strong navy. He dismissed plans for an A-Bomb as, "Jewish Physics." We were lucky that he had so many shortcomings. Many people don't realize it, but as he began his land war, the German Army wasn't even fully mechanized. Some vehicles were still horse-drawn. Yes..he started to fight six years before he was ready.
They still had horses till the end.
Scary isn't it. The US fought Germany and Japan with better equipment in many cases, but still had trouble.
The German Army that invaded Russia had 3,200 tanks and 600,000 horses. The Wehrmacht was never really totally mechanized.
The German Army that invaded France in 1940 was smaller and less well equipped than the French Army, not even counting a couple hundred thousand allied British troops in France at the time.
The relative sizes of the German and Japanese economies relative to their adversaries was something like 1:6 and even larger if you include access to stategic materials. The Axis was doomed by events of December 7, 1941.