The Germans getting the weapon first was the entire motivation behind the Manhattan project. It was known that they were working on it, and feared at the time that they were farther along than the US towards making it happen. To your point about Oppenheimer specifically, there’s a line in the film, where he’s recruiting one of the scientists to join the project. Oppenheimer says something to the effect of, “I don’t know if we can be trusted with this weapon, but I know the Nazi’s cannot be.” Whether he actually ever said this specifically or not, I have no way of knowing, of course, but it aligns with what I’ve previously read about the mindset of many of those involved with the project at the time.
Back to the movie itself…I cannot recommend it more highly. I think Mr. Nolan is perhaps the most interesting director working in Hollywood today, and he doesn’t disappoint here. To my way of thinking, most movies are just that…movies. Some are entertaining enough, and that’s fine. Some are awful. Some are pretentious nonsense. But some are truly art, and belong there alongside other art forms. IMO, Oppenheimer is just that. Cillian Murphy is perfect in the title role, and Emily Blunt is great as Oppenheimer’s wife. But of course, I’ve liked her work in everything I’ve ever seen her do.
I think @jpm mentioned this earlier, but to point out again - there are a couple sex scenes involving Oppenheimer and his former girlfriend, and a few times where her breasts are exposed. I didn’t find it over-the-top personally, but since this is a forum mostly frequented by Christian believers, I think that disclaimer is worth mentioning. I’m sure some here usually find such things in movies to be in poor taste, or at minimum it would impact whether you’d let your kids see it.