I assume this is about Nazism

I would think that it is about the horrors of Nazism. Kafka, who wrote the novel 'The Trial' lost his sisters in a concentration camp. Kafka never wrote directly. And this film doesn't spell out the Nazi significance either. A good film that needs to be watched again I would recommend.

It's more about the destructive power of blind, unfeeling, bureaucratic authority that's so labyrinthine & far-reaching that nobody can understand it, or escape from it. In short, a prescient vision of the late 20th Century continuing into the present, when individuals are lost & ground up in the mechanism of the system. From Kafka's early 20th Century viewpoint, he can see the alienation already at work in industrialized society, and how it must continue to grow & consume everyone eventually.