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 shit 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.