We weren't the only nation using any of those technologies. The Germans, for their part, were trying all of that. It was neither obscure or secret. Technical acumen in using commonly shared technologies was the difference.
It's why people like to forget there were three distinct phases to that war. Russia was not always on our side. The outset was bleak, the middle was indeterminate, and the end, the part we like to remember, was when the tide really started going our way.
In any case, we weren't invested in any of those things _before_ the war, so even if you do believe your premise, there's no reason to suspect that we wouldn't be able to do the same in the next conflict. Trying to prognosticate what the next war will look like has led to some embarrassing military defeats throughout history. The military fails to be egalitarian.
Speaking of proximity fuses you should look into what it took to _actually_ get them used on the battlefield as I think it highlights this point. In concert with that I like to think about the "Millennium Challenge 2002." War is won by skilled soldiers not by lavish spending or deep secret technologies.
The secrecy definitely played a major role when it comes to cryptography. It was not known to the Axis how far Allied codebreaking technology had come, and how much of their communications was being regularly monitored.
