Putting aside all unfortunate implications stemming from national socialism, you can see that the swastika symbol is present in cultures around the world, many of them isolated from each other. From the Americas to Ukraine to Scandinavia to Indonesia you see it with various regional twists. It also seems to very often have a similar meaning, one of prosperity and peace. What theories are there for why the swastika is so omnipresent in human culture?
As far as I know this is unsettled, but there's many theories for why it's so prevalent in cultures across the world.
Probably the simplest theory out there is that the Swastika represents the Sun. The four arms are theorized to either represent the 4 different seasons, or the revolution of the Sun. There's other theories as well though. It could be that there are multiple reasons for its origin depending on the part of the world its found in. Regardless of possible origin, what it symbolically means now also varies depending on the culture.
There's also multiple myths of ancient nomadic people who spread common symbols across the world. If I remember correctly, I think nazi mystics believed that aryans travelled to India and looked to Hindu myths to try to find out more about ancient pagan myths that had been lost. I don't know if there's any legitimacy to these myths, but I know that there's myths out there (not just related to nazi mysticism) that try to explain common symbols like pyramids appearing in various places by claiming they were spread by groups of wise travelers.