Oppenheimer's star started to fade at that point, although the public regarded him as a hero for ending the war. It all came to a head when the Soviets developed their own bomb and Teller pushed for an H-bomb as a counter. Oppenheimer actively opposed the H-bomb and his fate was sealed.
[Groves chose Oppenheimer because he needed a scientist to be the scientific director, because the science team wouldn’t accept an Army General, as their director. Oppenheimer was chosen because he was amenable to following Grove’s dictates as long as Germany and Hitler were the target. Groves was aware of Oppenheimer’s security problems but felt he could control his movement and actions with Army security personnel. When Germany was defeated before the bombs were ready, Oppenheimer led a group of scientists that petitioned Groves to do a demonstration test somewhere in the Pacific and invite Japanese observers to watch. Groves about lost it, no way he was going to breach security and inform the Japanese about the atomic bomb.
Oppenheimer’s star started to fade at that point, although the public regarded him as a hero for ending the war. It all came to a head when the Soviets developed their own bomb and Teller pushed for an H-bomb as a counter. Oppenheimer actively opposed the H-bomb and his fate was sealed.]
There is lot more to that story and it was brought out in the film