Also maybe losing all scientists to America and half of the country to Russia for 30 years might have contributed here.
A cultural aspect may be that Americans are more willing to try and fail, which in software has almost zero cost. In engineering it's an advantage to be risk-averse. In software where "building" is automated, and barely a factor. Theory almost equals practice here. So it's cheaper to practice.
Population of Germany:
Population of the USA: Population of the world: So, they may have stayed equally innovative per capita, but in 1940 about 1:33 of humans were German, while in 2020, that was 1:94.