Why did Robert Oppenheimer not win a Nobel Prize in Physics and John Nash not the Fields Medal?

Question

considering that alfred nobel himself contributed to destructive technologies...

Answer 1

You could ask the same question about a number of other scientists, and the answer is simply that the contributions of others were deemed more important. It certainly was not censorship because his work could lead to weapons - the Nobel prize WAS awarded to the man who actually sustained the first fission reaction and hence directly paved the way to the atom bomb. And this man - Fermi - also worked on the Manahatten Project.