> Hitler was not that far from a nuclear weapon.

Where did you hear this? Hitler wasn't anywhere close to a nuclear weapon, Nazi Germany lacked both the necessary theoretical nuances and industrial capacity to create nuclear weapons. Even if they magically had made one, they lacked a credible delivery system for it which is its own enormous can of worms especially in the early 1940s.

Even Britain which did have good theoretical foundations and even a headstart on the American programme was obliged to merge its efforts with the Manhattan Project because it lacked the resources to do it so quickly alone. The largest empire on the planet at that point couldn't fight the Second World War at home and develop the bomb fast enough to be relevant, the Nazis had no chance.