GDP growth does not mean increased prosperity. When the transactions are through coercive force rather than mutual agreement, prosperity is destroyed, not created. That's the failure of socialism. Guns & Tanks != prosperity.
We could have a massive boost in employment and GDP if the government employed 3 million people to dig holes in the ground and fill them back up, but we'd all be materially poorer for it.
That's what happened with communism for 60 years. You had full employment and great GDP numbers year on year, but you still had to queue for 2 hours to by a loaf of bread. Eventually it collapsed in on itself.
That's what I was saying before mate , it was an unsustainable economic policy based on financial slight of hand , massive rearmament and as you say in simplistic terms building roads. These magnificent financial policies without German expansionism would almat certainly been unsustainable in the long term.