It's not terribly surprising that this initiative won, of course, as it was prominently opposed by leaders of both major parties in the state at a time when they're historically unpopular. I imagine the calculation many voters made was, The parties hate 14, I hate the parties, ergo I like 14. Indeed, it's fitting that the initiative passed in every county save two -- Orange County and San Francisco, probably the two most openly partisan counties in the state and the hearts of the state's Republican and Democratic establishments, respectively.
All this said, I'm actually curious what will happen, assuming the lawsuits against Prop. 14 fall flat. We actually don't have very many cases of states trying this sort of primary system. Maybe it will measurably reduce legislative partisanship. And while California's own history shows weak partisanship to be dangerous, the state currently has partisanship to spare. Of course, partisanship is far from the state's major problem right now, but at least from a research perspective, I'll be watching to see what we can learn.