The theory isn't really the hard part, as a practical matter: making the Nuclear bomb in the US took over 30 project sites and over 100,000 workers, and about $36 Billion in today's money, and the US wasn't being bombed during development.

Germany, by contrast, hadn't even finished expanding its conventional factories at the start of WW2, and its entire warplan required the war to be over by the start of 1943, as Germany would simply run out of fuel if that wasn't the case, and could do little more than gradually lose.

The Germans were fully aware of all of this, and any work on a nuclear bomb was basically cannibalized for use in other projects. By 1943, an effective Nazi nuclear bomb program was about as realistic as gaining air supremacy with jets, so it didn't really matter what fantasy project Germany pursued.