The proposition that made California the way it is is the one that meant that the primaries are non-partisan and the final race is between the two top contenders. This means that special interests in California need only present their cause through the lens of leftism and they will automatically find sympathetic candidates in the top two, no matter who those are. Contrast this with a partisan primary system. In that system, on the final ballot, it would be difficult for special interests to formulate an argument appealing to both candidates.
EDIT: for some reason, I am downvoted but there is little engagement or actual refutation of what I'm saying. If you're going to downvote, at least say something. Otherwise, it makes it seem like the one-party state's propaganda arm is awake and working.