She probably would have still won the nomination without California. The DEM primary process is rigged through having a large percentage of super-delegates and proportional allocation of state electors. You could lose every state in a head to head match up and still win the nomination because you would get about 40%-45% of the state delegates coming in 2nd. Just need the supers to come over. The Supers mainly vote according to what the party bosses say, because they are the ones who dole out campaign cash, organize endorsements, issue the plum committee assignments, keep challengers at bay etc. The Party Bosses choose the candidate who raises the money for them, or otherwise strong-arms the party brass - greenmail, blackmail, threats & intimidation, carrots & sticks and the like.
The DEM party should never have nominated Hillary and yet she finagled the process by filling the party seats with her lackies (many of whom also received money from the CGI either beforehand, or afterwards, in what looks like yet another quid pro quo arrangement), commandeering fundraising, holding onto 900+ FBI files and the like. Plus, her email and pay to play scheme probably entrapped everyone from POTUS on down, forcing them into no other choice but to support her to save themselves.