I'm going to quote my own answer from this thread as I think it provides the answer you seek.

Prior to the Nazi party, the swastika was not an unknown symbol in the West. It was associated with luck and charms in many parts of the world - however it never had much wide spread adoption as a major religious symbol.

Prior to the rise of the Nazi Party the swastika had been adopted by ex-Baltic soldiers who learned of the symbol from Finland during the Great War, or World War 1. These same soldiers adopted the swastika as their symbol in German Nationalist groups during their opposition to the growth of opposition to the post-war German Republic.

Some anthropologists at the time also believed the swastika to be of Aryan origin, and that it's spread followed the spread of Aryan people across Europe and Asia. They dated archaeological finds to make the 'Danubian Culture' older than the other south-eastern cultures who also used swastika and to establish a kind of Indogermanic origin for European and Asian culture to spread from.

Adolf Hitler recognized the powers of symbols and pushed the swastika strongly, while at the same time carefully preserving and cultivating it's use. He was very aware of the symbols use among German nationalists already and association with Aryan culture.

The Swastika - The twilight of a universal symbol by W. G. V. Balchi (Interestingly this was written during the war, and the author laments the impending suppression of the symbol)

The Swastika; Its History and Meaning by John Prince Loewenstein