Hitler did not choose the symbol because it was "anti-Semitic". Nowhere in the web article you cite in the comments does it say any such thing. It says, quote, the swastika "...traditionally had been a sign of good fortune and well being...". What the article says is more or less correct. At the time the swastika was an extremely common decoration and symbol both in India and China. Originally it was probably a symbol for the sun, but by the 20th century that was long forgotten and most Chinese just considered it a "good luck" symbol. In 1920, you could find the symbol on every street in Shanghai.
In the United States, the swastika was perceived as an exotic, ancient symbol and associated with mysticism and kitschy fortune telling. At the time there were many cockeyed theories about "secret, forgotten ancient civilizations". Here is a typical example of a magazine article writing about such theories as though they were fact:
[After the flood] we find a brown-skinned people establishing parallel
civilizations in fertile lands close to the shores of the inland
sea--the Mediterranean. We find the Sumerians in Mesopotamia, in the
valley of the Tigris and Euphrates, and the Egyptians in the valley of
the Nile. And, what is strangest of all, we find traces of the same
sort of people and the same sort of culture, distributed in far
separated lands--in India, China, Central America, Mexico, and even in
England. Distinguishing this culture are certain common
characteristics, such as the building of crude stone (megalithic)
monuments, the making of mummies, and the use of the symbol known as
the "swastika" for good luck.
Popular Science August 1925
So here we see in Popular Science an example of one of these nutty amateur anthropological theories parroted as though it were a well-accepted fact.
In the Great Gatsby, the character Wolfsheim is given the word for his company by the author to evoke a sense of exotic, mystical superstition. For example, Wolfsheim has cuff links made out of human molars, another example of his weird, superstitious nature.