I propose that California's poverty woes are disproportionately due to a permanent and ever-growing underclass, whose existence and continued plight isn't caused by policies like rent control, welfare reform, and targeted eco-taxes that end up being regressive; but rather, is a simple consequence of individuals desperate for more prosperity and financial security making tough choices for the good of their families.
They are attracted to the cores and fringes of urban areas that play host to islands of productivity and wealth, where they work long hours and multiple jobs in an effort to provide. Some are later-generation Americans born to immigrant ancestors, some are youth from elsewhere in the US trying to flee metros with no growth, some are recent arrivals from regions of the world plagued by poverty and strife, and some are undocumented, working under the table and living in the shadows of mainstream society, more avoidant of law enforcement than groups who suffer the most violence at the hands of the law, and always at the mercy of their employer, handlers, and pure luck.
These groups are there because in California they can capture a larger portion of the effects of trickle-down than in North Carolina, Texas, or New York; and because the state-provided safety net, average people's compassion, and availability of human connections and capital allows them a small, but more meaningful chance of breaking out of the poverty trap.
In other words, the prosperity, concentration of wealth, human capital, and laxer attitude of California allows these marginalized groups a better shot than elsewhere -- especially places like Mississippi and West Virginia, whose poverty is primarily indigenous, and isn't among recent arrivals. California is somewhere where trickle-down does display elements of it working, at the very least in the hearts and minds of those attracted to the state. We can argue about its magnitude all day long, but to flagellate all manner unrelated policies after a myopic reading of statistics is absurd.