Hitler and the Nazis in general had a really weird racial philosophy. While the "Aryans" were considered the master race, the Nazis had a weird relationship with Asians where they saw parallels with the descent of the Aryans from the Nordic gods.

Pride in one's own race – and that does not imply contempt for other races – is also a normal and healthy sentiment. I have never regarded the Chinese or the Japanese as being inferior to ourselves. They belong to ancient civilizations, and I admit freely that their past history is superior to our own. They have the right to be proud of their past, just as we have the right to be proud of the civilization to which we belong. Indeed, I believe the more steadfast the Chinese and the Japanese remain in their pride of race, the easier I shall find it to get on with them. - Adolf Hitler, 1945

There was always this weird Asianophile mentality in Europe that China and Japan had many thousands of years of civilization. For instance, the SS sponsored an anthropological expedition to Tibet, where it had been thought the Aryans may have descended from the land of the gods.

After the post-war period, many members of the former German military went abroad. A large number of officers and other officials ended up working in China and Japan. These officers also tended to have very strong, Nationalist tendencies, and were often reactionary if not fascist in political outlook. For instance, Max Bauer, one of the first leading German experts in China, had Nazi sympathies, Hans von Seeckt, former head of the German Reichwehr, was extremely reactionary, and John Rabe, the man who is credited with saving up to 250,000 Chinese during the Nanking massacre, was a card-carrying member of the Nazi Party. In a sense, this created a pseudo-China lobby in German politics.

Hitler operated a bit strangely: everything he did was for the one purpose of building an army strong enough to conquer the Eastern lands. For instance, he purged the SA, despite the SA being a loyal support group of Hitler, because the SA was looking to supplant the Reichwehr, and Hitler needed a professional military to successfully conquer Russia. In that line, he needed military support from anybody that was willing to take action against the Soviets. Both the Chinese and the Japanese were anti-Communist, so he saw them as useful allies to flank the Soviets: however, when Japan and China went to war, he picked Japan over China because he felt Japan would be more useful in the immediate timeframe of the German invasion.