I felt the same, my thinking at the time was they didn’t want the bomb to steal the show. The movie was about the man not the machine.

/hah very articulate of me for this early in the morning

I suppose that's true, but it's still positioned as the focal point or climax of the film I think.

But Nolan intentionally hamstrung himself by eschewing CGI in favor of practical effects. I mean in theory you could do a practical effect of a nuke but that requires detonating a nuke; the west hasn't done that since 1992, the last nuclear detonation was done by North Korea in 2017.