California is broke because of Prop 13. It basically cut out from under it the main funding mechanism for the state government property taxes and then put severe limitations on how the state could raise funds through other mechanisms by making any tax increase in other categories like sales tax or income tax too difficult to enact. As such the previous high-tax/high-service government that Californians enjoyed became unstainable.
Additionally, due to the initiative system the state has almost no control over it's finances. Something like 70% of the budget is mandated spending by initiatives, with a large portion of the remaining 30% either things you have to spend money on like police, or required via Federal funds. It's why to pass a budget every year they always need to resort to some tricks. And with the requirement that they need 2/3rds majority to pass any budget, instead of 50%+1 like every other state in the union, means the minority party has no interest to negotiate.