>>212733627 (OP)What is it with you zoomers being offended by sex scenes
To answer your question, the movie is about the things that haunted Oppenheimer, his decisions and their consequences both for himself and others. The affair with this woman, who later took her own life after he rejected her, and which became known to his wife, was one of the things that haunted him.
The real question is why they showed so little about the actual devastation of the bomb, we see like one hallucination of a burned Japanese person and that’s it.