SF-LA ~380mi is actually a real sweet spot for HSR.
Flight time of 90 minutes but the hassle of getting out to airport, check-in, boarding.. and then the opposite on the other end makes your all-in travel time about 4~5 hours. With HSR you are generally going city center to city center, and 380mi is achievable in 2~2.5 hours all-in.
I took a 700mi HSR in Japan that was probably on the very far end of being competitive time wise with flying and was still great. 5hr train vs 2hr plane segment, but all-in door-to-door travel times were comparable (5h45m vs 5hr).
Train 5hr45m door to door with majority of time sat in a comfy quiet train with big comfy seats and high speed internet. A flight which is 5hr door to door is mostly a ton of hurry-up-and-wait with small blocks of 30-90min here or there you can read a book.
Your business class traveler from LA/orange county to SF bay is already well served by the many airports in both metro areas.
the HSR is about connecting the rest of the state to economic opportunities in these large metro areas