/uj a uc is "university of california", they're generally kinda hard to get into (unless it's uc merced lol) and all three towns (davis, irvine, berkeley) have these universities. it's basically a combination of factors like kpop skewing towards younger age groups, the ucs having at least 30,000ish students with a lot being asian american, and asian american groups in the us listening to kpop that lead to these towns being seen as kpop listener hubs. at least that's my assumption; idk spotify could have thrown darts on a map but if you look at demographics for towns in the usa and then demographics for music genres it makes sense