I don't think the likable story is key. Until recently, most of the many millions people buying the sauce didn't know anything about its origin. It was just the cheap sauce alone in its category that you could find everywhere.
I've got two different blends of Sriracha sauce in my cupboard, both from Thai companies and one of them even copying Tran's bottle style, but it wouldn't have occurred to me until reading this article that a particular Vietnamese-American brand was supposed to be the "authentic" one. He could have got the origin story out there to people who don't watch documentaries about hot sauce if he'd spent money on advertising though...