If you are embarking on such a Keynesian program in a climate of general depression and lack of investment in other countries then you will enjoy generally low

If you are embarking on such a Keynesian program in a climate of general depression and lack of investment in other countries then you will enjoy generally low interest rates but you lose the ability to make short term investments and must make longer term ones. In the case of Nazi Germany Hitler purposely took on massive amounts of debt to rearm the country. Any economic success was temporary and entirely dependent on the massive arms program. Not only was the Nazi state inefficient arms investment couldn't possibly have ever paid back the investment in borrowed money that created the Nazi military.