I suspect like other globalists, Madame Halfbright included, that he was against the US being the only super power as we weren’t to be trusted. They wanted the Soviets, now Russia, to have the bomb to balance our power.
That was the early rational for giving away secrets of the bomb to the Russians... it was a lame excuse planted by Russians into smart but totally naive American scientists. Russians played on the egos of men who should have known better - telling them they were saving the world by undoing some of the damage created by their awesome knowledge. It was pure flattery and manipulation. Because of these idiot scientists we lived under the fear of total nuclear annihilation for decades. And the Russians spread the information to many totalitarian thugs... I'm surprised anyone is still parroting that old soviet garbage.