To some degree, I think the time was simply right for Star Wars. The Sci-Fi of the sixties and early seventies tended to be quite dystopian IIRC. SW called back to the old space operas and the serials, and generally was more heroic and hopeful than what audiences had had with films about social breakdowns and Cold War analogies. The aggressive marketing campaign and merchandise didn't hurt either. I still remember to this day going to a department store and seeing actors dressed as Vader and a Stormtrooper, just days after the movie released.
Just my
