That's the plot of like half the comics Lex Luthor appears in -- the difference this time was that Luthor's crazy invention, an "atomic bomb," was actually in the works in the real world.
Set to run in late 1944, almost exactly a year before the world found out what an atomic bomb was in a big way.
While the comic was being written, scientists were secretly working on the first A-bomb. To maintain the secrecy of the project, the Defense Department ordered DC Comics to pull the story. Yes, apparently, the Pentagon feared the Japanese might see the comic, go, "Holy s**t what if that's a real thing?!" and then build anti-nuclear domes around all their cities. Or something.
This was, more or less, their line of thinking.