Surveys typically suggest that only about 10 percent of the homeless in California come from elsewhere. This leaves 90 percent of them as Californians who had a home there at one time.
Thanks in part to the lovely weather, California has the most unsheltered homeless. IIRC, it also has the most chronic homeless.
I spent nearly six years homeless, most of it in California. I left the state to get back into housing someplace cheaper.
I strongly suspect that the insane California housing prices are a major factor here, much more so than mental health issues or addiction. For every 100 poor families on the West Coast, there are only 30 affordable homes. [2]
California has about 8.5% of the US population. There is something very wrong that it has 25% of the homeless population.
[1] https://en.m.wikipedia.org/wiki/List_of_states_and_territori...
[2] https://www.geekwire.com/2018/every-100-families-living-pove...