The most caricatural example was Heisenberg, who was working on the German nuclear program, made a lot of experimental mistakes (he was a very good theorist, an average experimenter) and it turns out that his assistant, who had been designing a lot of experiments, was Jewish and had fled a few years before.

He made a crucial mistake in an experiment that was supposed to gauge the amount of uranium necessary to make a bomb. He failed to take into account impurities in a material. It made him assume the crucial mass necessary was 10x what it is.

Ultimately nazi Germany, after several drawbacks, decided an atom bomb was too far away to pursue.