In addition to climate change/increase in fires and other occurrences, there is the corporate greed and "scare" factor.

As a CA homeowner since 1980, I've seen the premiums fluctuate. After the 1991 Oakland Hills fires, the rates skyrocketed, with State Farm pulling out, but rates eventually settled down (and chicken-little State Farm was back...note they had a poor "claims paid" record, and I have nothing to do with them).

As with CA oil and lumber prices, the industries use consumer fears as a means to jack up prices (ie the "old growth redwood scare" of the early 90s, various "Arab Oil Embargo", "Refinery Fires", and "Supply Chain Issues" rather artificially jacking up prices).

Thankfully, capitalism generally defeats these artificial spikes, as alternatives present themselves. How far could these home insurance spikes go before homeowner groups decide to "self insure" at cheaper prices (along with better internal protections such as secondary water sources and better defensible spaces). Self-insurance pools (with farmers for instance) is how the insurance business evolved in the first place.