except it wasn't. the french had colonial troops who went on rape and other crime sprees every time they could. That's why the germans knew. If you're open to that level of negrophilia in the first place, your country's destruction is an inevitability
Couple that with the fact that the French had occupied Germany with tens of thousands of nigger military straight from Africa, who committed countless rapes and forced Germans to build and populate brothels for them, it was extremely clear to see that the white race had given up and willingly gone extinct even in the 1930s.