Either that story is not true or it is beside the point. Nuclear fission was the huge topic of physics research in the 30's and the potential to weaponize it was widely understood by physicists, and the government aggressively funded it (the government mind you, not private companies). To say that nuclear physics was considered an irrelevant field by the scientific community in the 30's is just not true.

http://en.wikipedia.org/wiki/History_of_nuclear_weapons#Phys...