I heard that the reason was to identify Germany with the Aryans, the first known users of the symbol, and instill racial pride.
The sad thing is (and shows how we stupid humans can so easily be lead by
a charismatic leader) if you hold Hitler, Himmler, Goering, etc up to their own
aspired Aryan ideals...blond, blue eyed, firm buttocked....all these nutballs
fail their own test!
Even if the Fascists had won, sooner or later someone would have noticed
this fact.
Cheers
Elras.