But only American citizens can vote. And I can't seem to find any data on the increase of the California population from naturalized citizens.
Prior to 65 immigration act, California was over 90% white.
By 2010, non-hispanic white was down to %40, hispanic ~%37%.
That is a huge demographic change. Hispanics nationally vote for Democratic/liberal politicians on avg. 70%.
So.. ergo, the dramatic blue turn California has taken politically can be accounted for by drastic change in demographics.
Your first statement is just restating the same premise: a dramatic change of the makeup of the electorate (whatever their "needs" or preferred political policies) changed the outcome of elections.
https://en.wikipedia.org/wiki/Demographics_of_California
section: "Population of California according to racial/ethnic group 1960–2010"