A nation that feels no shared sense of history —a gaggle of grey, monochromatic mutts— is MUCH more easily dominated by an organized minority:
They have nothing to pull them all together to cast off their chains.
I believe that you and I are on the same side, but I must dispute your characterization of Germany as devolving into a society of grey, monochromatic mutts.
On the contrary, the goal is "Divide and Conquer." A homogeneous society of like-minded people sharing a single language and culture, etc. is difficult to subvert and derail. On the other hand: An extremely heterogeneous conglomeration of competing and opposing splitter groups can be taken into any direction its masters choose.
Regards,