Non-profit insurance options would be a great step in the right direction, but they would not address most of the underlying reasons for high insurance costs. Non profits would be reading the same actuary tables for profit insurance is working with, and would need to meet the same regulatory requirements to operate in California.
On the insurance industry side nothing short of government subsidy would make the books balance if we had another 2018 or 2019. To address insurance costs we need to look beyond insurance and address things like the high cost of building materials, and zoning that allows residential construction in high risk zones. Often it's hard policy decisions that are not popular with voters that would actually lower premiums.