Any German with any Jewish heritage whatsoever was pushed out of Germany in the 1930s. Those in academic posts lost their positions — and many of them emigrated. Many of those folks landed in the US, which gave physics and chemistry (Fritz Haber) in the US a real push. There’s a quite readable book about this: Hitler’s Gift.

Also remember that, however much US science was pushed forward, Germany got retarded by the same or more.

…he was a pretty good leader

Actually, he wasn’t. He liked to have multiple people and departments competing for his favor. For instance, the German pause that allowed the Brits to escape at Dunkirk came exactly from this competition between ground forces and aviation.