Utterly irrelevant as I said - no one is creating nuclear powered ships (or nuclear powered anything for that matter) in the 20s - it took until the late 50s before it was practical.
And Germany was not the leader in theoretical and experimental physics in the 20s - it was one of them certainly.
And none of the other leaders - UK, USA and France would have been remotely capable of this feat of advancing this technology by 30 odd years either.
Well from the first one in 1901 until the outbreak of ww2 Germany had 10 nobel prizes just as UK. 12 if we count Austria which you might in this context. US is third with 7. Add the specific names Einstein, Heisenberg, Hahn…
You might even add Oppenheimer who did his PhD in Gottingen from 1925-27. Maybe ITTL he gets to work on the project.
The timeframe. It takes 4 years from the theoretical Foundation in 1938 and less that two years from the first 6000 USD donation in 1940 to the first sustained chain reaction. Then and after 1945 the focus is 100% on making bombs, but the first electricity producing reactor came in 1951 and nautilus in 1954.
If electricity producing nuclear power is the overarching goal, I think 30 years from fission Discovery in the 1920’s is very pessimistic.