Why are the Japanese, in Hitler's theories, a "culture-bearing" rather than a "culture-creating" people?

In Mein Kampf Hitler puts forward a fairly crude tripartite hierarchy of races. At the top of the pile are the Aryans, what he refers to as the "culture-creators:" the superior race responsible for every great work of art, every scientific and technological advance. Beneath the Aryans are the so-called "culture-bearing" races. According to Hitler, they are incapable of creating anything of lasting importance; however, they do have the ability to adopt and assimilate aspects...

In Mein Kampf Hitler puts forward a fairly crude tripartite hierarchy of races. At the top of the pile are the Aryans, what he refers to as the "culture-creators:" the superior race responsible for every great work of art, every scientific and technological advance. Beneath the Aryans are the so-called "culture-bearing" races. According to Hitler, they are incapable of creating anything of lasting importance; however, they do have the ability to adopt and assimilate aspects of Aryan culture. He says the Japanese are one such example of this. Without the benefits of Aryan science and technology, the Japanese will sink back into their previously primitive state. As they lack the ability to create culture, they would lack the inspiration provided by the Aryans to develop and advance.

Nonetheless, Hitler pays tribute to the Japanese in relation to foreign policy. He credits them for making an alliance with the British in 1902. This gave them the backing of a powerful European ally, which enabled them to successfully defeat the Russian Empire two years later. Hitler contrasts the conduct of the Japanese with what he regards as the stupidity of the Germans in allying themselves with the decaying, multi-ethnic Austro-Hungarian Empire. Had the Germans showed the same foreign policy nous as the Japanese, then the First World War could well have been avoided.

Hitler's recognition that the Japanese, though still only a culture-bearing race, had positive qualities nonetheless, undoubtedly played a part in his decision to ally the Third Reich with Japan in the wake of Pearl Harbor. Though Nazi ideology regarded the Japanese as racially inferior to white Americans, we can at least explain the rationale behind Hitler's decision to declare war on the United States. The Japanese, though considered inferior, could help the Germans to achieve its geopolitical goals, especially in relation to its projected conquest of Russia.

What this indicates, among other things, is that Nazism's racial categories were not so rigid that they could not be adapted to the changing circumstances and necessities of war.