Not relevant just to Asian faiths, as it was a symbol widely used in many Indo-European cultures, particularly Slavic and Roman(and Germanic, but that perhaps hits too close to the problem). You still can see it as ornament carved into wooden beams under a roof and above doors on many old houses in rural areas of Serbia and Romania. Not sure though if it had any real superstitious meaning after the Christianity came, or it was just a traditional ornament that continued to be used purely as a decoration.
Like heaping earth to build which leaves only so many possible forms (like pyramids) there are only so geometric patterns before things start getting massively complex. Just like the Swastika, the hex-star (seal of solomon, star of david), the cross, & the pentagram (which are all very ubiquitous), these are things you would discover yourself looking for interesting geometric figures, likely quite early in your search for designs. It seems to come down to angles that were easily measurable, like (in degrees) 30, 45, 60, 90.
Only just reading this now and wondering if you've any reference regarding its usage in Ireland. The only non-Nazi usage that I'm aware of is the Swastika Laundry (I used to work nearby and unforunately, the swastika is now gone from its chimney stack). When I researched it, it turns out that the founder was inspired by an ornament he saw at the 1910 Great Industrial Exhibition in London: https://www.nationalarchives.ie/article/behind-scenes-swasti...
With a layman's interest in history, religion, iconography (and a multitude of other areas that I don't have enough time for), I'd be interested in learning about other or older examples of swastika usage in Ireland. So far, I've found this wonderful blog post: https://rmchapple.blogspot.com/2017/10/always-remember-to-dr...
