Two Wild Mass Guesses — the world of The Grasshopper Lies Heavy is a skewed vision of our world, and The Man In The High Castle is a skewed vision of a real alternate world where the Axis won.A little confusing, I know, but bear with me. Both The Grasshopper Lies Heavy in the book and The Man In The High Castle in real life were written with the aid of the I Ching, with each and every plot development decided upon by consulting it. In the book, this results in The Grasshopper Lies Heavy, the story of an Allied-victory world that is rather over-the-top and somewhat implausible in just how total this victory is. And in real life, this resulted in The Man in the High Castle, the story of an Axis-victory world that is rather over-the-top and somewhat implausible in just how total this victory is. So the WMG is: not only is The Grasshopper Lies Heavy a skewed and flawed look at our world — the real world — as seen through the I Ching by Hawthorne Abendsen, but The Man in the High Castle is a skewed and flawed look at an Axis-victory world — an equally real world — as seen through the I Ching by Philip K Dick. And just to extend the WMG a little more: in that real Axis-victory world, circa 1962, an author named Hawthorne Abendsen wrote a novel called The Grasshopper Lies Heavy, which featured a book-within-a-book called The Man In The High Castle written by a fictional character called Philip K Dick...
The Man in the High Castle in an in-universe Japanese novelWhich is why it has bizarre I Ching and reality-related themes and the Japanese are portrayed as being fairly nice compared to the Nazis despite the fact in reality they were as cruel and nasty as the Nazis (see the Rape of Nanking for example).
People in The Man in the High Castle are slowly losing their collective grip on reality due to the stress of living in a world where the Axis won.The devotion to the I Ching, the hallucinatory scene where the world suddenly shifts into another alt-history where the Allies won, the presence of The Grasshopper Lies Heavy, and all the overcomplicated social maneuvering point to something being very fundamentally off with human society. The madness of really living in the Axis power's dream is too much for the collective of humanity to handle, and that's why the Greater German Reich and the Greater East Asia Co-Prosperity Sphere are going to mutually annihilate each other right after the end of the book: Not because they are both superpowers, and not because they believe each other to be inferior, but because humanity has developed a collective death wish that makes such an obviously suicidal course of action look good on a subconscious level.