I cant speak for the US but Stax have been very well known in Europe for several decades and i've been a user of their products off and on for over 40 years (showing my age now ).
I still have the original pair of SRD5's and energizer I bought all that time ago. They still work fine and the energizer was repaired once in all that time!
Now thats what I call value for money.
The internet has been huge to popularize them, specifically the Head-Fi megathread and other headphone forum megathreads. They would have had next to zero international presence otherwise given how they marketed themselves. If they were founded during the internet/forum age, they would have had a whole lot of immediate international hype with the quality of product they put out. As it is, they languished in relative international obscurity for a long time.