How do so many Korean businesses in Fort Lee and Palisades Park stay successful if they're mostly serving other Koreans?

When you walk around Fort Lee or Palisades Park, there are tons of Korean restaurants, bakeries, cafes, salons, grocery stores, karaoke spots, and other businesses. A lot of them have Korean-only signs or menus and it seems like they're primarily geared toward Korean customers. I was just in Pal Park earlier and couldn't help but notice that there was not a single sign in English and besides that one pizzeria on Broad Ave, pretty much all the businesses from salons to restaurants are pretty much catered to only Koreans.

From a business standpoint, doesn't that limit your potential customer base? Koreans are only a small percentage of Bergen County's overall population (and I think smaller than the Hispanic population), so I'd assume expanding beyond one community would make more financial sense.

Yet many of these places have been around for years and new ones keep opening.

Is the Korean population in this area just large and concentrated enough to support them? Or do a lot more non-Koreans visit these businesses than I realize?