Basically, most Californian Asians are at least 2nd or third generation, and probably more than that, so they're far more likely to vote than Asians in say, Georgia.
I think this greatly underestimates the volume of recent (post-1960s) immigration as a share of the total.
I'm not from California, but I recall growing up assuming that most of my native-English-speaking Chinese-American classmates were descendants of people who built the railroads in California 120+ years earlier, but no, mostly their parents had gone to college in Taiwan or China and come over in the 1970s and early 1980s. And in California, you have enormous Filipino, Korean, Vietnamese, Hmong, and South Asian populations that necessarily post-date WWII.