I've always thought California could trend insanely D even when Dems were winning it by big margins and even before Trump ran as a white grievance candidate.
If you look at the fundamentals of the state it's basically the epitome of a Democratic trending state. Lots of big cities + extremely educated suburbs. Whites were already very liberal in the state. Fast growing minority populations. Lots of immigration. Lots of colleges/young people. I can't think of any demographic that has been growing in California that is Republican-friendly. I guess it's getting wealthier, but they're not the kind of wealthy voters that find GOP policies appealing. I think that Trump loses by 2% more no matter who the Democrat is on the ballot in 2020. Though I do think Hillary was a particularly strong candidate for California (she seemed to do well with Hispanic and Asian voters in particular).
Why are California whites so liberal?
Because of the SF Bay Area and LA County. Highly populated, highly educated metros with big tech and entertainment industries respectively. Outside of SF and LA, Cali whites are strongly R leaning, including in SoCal. If California had 1940 demographics it would most likely be a Romney-Clinton state. A lot of CA whites in LA are jewish so that's part of it too.
