Never heard of the Nuremberg trials?
Never heard of the mountains of evidence which shows that Earth is round beyond any sane doubt, putting to rest any sane notion of a conspiracy?
If that doesn't stop people what makes you think something like the Nuremberg trials would?
Remember, people that believe in conspiracy theories would go quite far with less than sane ideas.
Also, you will have to explain how a guy like Hitler, at fist a commoner, slowly raised to power by shouting for the death of America and Europe his whole life BEFORE he was elected president; was suddenly trusted by America and Europe to such a massive secret.
Again, it comes down to how much was set up?
Was he truly a commoner that grew to power?
Or was he actually acting right from the start?
Or were some of the details of his childhood "altered"?
Or did he really just want power and riches, and when gaining it was approached by the Americans that agreed to help if he joined them?
You also overlook a big issue, if they did approach him, and he didn't agree, I doubt he would try to "reveal" the secret, as he would just appear to be crazy.