Anyone politically involved enough to risk the serious penalties for fraudulent voting would know that it would make absolutely no difference at the Presidential level in CA.
Clinton won CA by 29%. WHo would risk 10 years in jail to make it 29.000001%?
It's the swing states where the stakes are high enough to motivate fraud.
The fraud is incidental and cumulative: It is what turned California from staunchly Republican to pervasively Democrat. Now it is inherent and automatic (e.g., motor voter, et cetera).
Without fraud, the only other explanation is that millions of conservatives and moderates moved out of the state, and that the huge majority of people who moved there since 2000 are liberals.
Clinton MIGHT have won CA by 10%. Voter fraud at a massive level made it 29%, and likely brought a few other seats to the 'rats at both the state and federal level.
Both are damaging; and if dems ever get their way, all it will take is for a few mega-cities to swing the entire election, which they'd love cause it's much easier to cheat in a few highly populated cities they are in charge of, instead of cheating in numerous cities in numerous states, some of which they don't control. Taking it to extremes, if the Electiral College were gone, a Republican could then narrowly win 49 states...yet lose the election when the dem wins CA by a vast margin!