And...so? California has dense areas in the north and south and a big (relatively) empty gap between them. California HSR is designed to connect those dense areas. The overall density of the state (or the corridor) is pretty much a side issue.
And, if your city is not on the Acela route, you may well be able, due to the area's density, to take a commuter rail or another train to get to a city that is on the Acela route.
Similarly for Acela's Boston-NY route -- New Haven is on the route, so people from Connecticut can likely get to it.
And, of course, people in NJ can easily pop into NYC and grab Acela as well.
By contrast, the lack of density in CA would mean that aside from LA - SF (and a bit of traffic to and from Sacramento), you wouldn't likely have that sort of potential passenger-base.
Actually, since California has a large total population, and its mostly concentrated in a few major urban areas, what that means is you have a natural constituency for high speed rail with few stops, spending more time at speed.
LA (and San Diego) to SF (and Sacramento) is a lot.
There might be a bit more interaction between LA's entertainment industry and the Bay Area's tech industry, but how many additional people would be travelling for this purpose?
I expect that, given that the northeast corridor comprises the nation's capitol, its financial capitol and its academic capitol (the latter two also being high-tech centers), one would expect movement between these places and would want high-speed transport.
I just don't see a similar dynamic operating in CA. Sacramento cannot compare to Washington, D.C. and LA and SF are pretty self-sufficient, as I expect San Diego is as well.