Similar cultural enclaves exist elsewhere in the world and are presumably similarly effective, but they just aren't as large a portion of the population.
Even small cultural differences can have outsized effects because of pollination-- e.g. it's easier to learn from an expert in a domain if there are more experts around you.
I think your question isn't really that much different to asking why the bay area has "punched above its weight" in terms of producing successful tech companies compared to other regions around the US... or why other regions have had a lot more success in other domains.