Why did hitler belive the swatstika embodied anti semitism

Answer: symbol of swastika was used by so-called "Volkisch denken" (Volkish thinking), modern mystical tradition that existed already at the very beginning of the 19th century. It was kind of mystical and at the same time nationalist kind of thought. Hitler decided to use element of this Germanic mystical thinking. Doing that he seduced many of its representants.

Explanation: Volkish thinking has to with believe in Germans as "Lichtmenschen" (people of the light, people led by Solar principle who are creative and have instinctual divine calling in contrast to Jews who are "arid" and "baren"). There are many people in German tradition who can be considered "volkisch" like Lagarde or Julius Langbehn or later Arthur Moeller van der Bruck who invented term "Das Dritte Reich" (the Third Reich).