@vapaad I have not seen the film yet. I never met Oppenheimer. I did attend a lecture by Edward Teller in which he was asked about Oppy. I won't quote him, but his defensive answer left me with the impression that none of these guys were heroes.
IMHO:
The mindset of the scientists of the time is most clearly captured in Kurt Vonnegut's book, "Cat's Cradle." For better or worse, their toying with the destruction of global civilization was mainly "play," until the Trinity test.
As a science teacher, I explained the process of nuclear decay on the blackboard, and the principles of fission and fusion. It wasn't until I visited the research reactor at Oak Ridge and stared down through the pure water in the "swimming pool" at the eerie blue-white glow in the core of the reactor, and felt the heat on my face, and saw the Cerenkov radiation from the spent fuel rods, that nuclear energy became real to me. I suspect that something like that was true of the physicists of the time.