I moved out of California almost five years ago, and even back then, it was difficult to get home insurance.
Basically:
1) Wine Aunts in California elected Gavin Newsom because he has an astonishingly great haircut and he owns a treadmill
2) Ralph Nader is a dumb cunt. He contribute a great deal to the destruction of the US auto industry. He was responsible for the Iraq War, by tipping the scales of the Y2K election, leading to George Bush getting elected. And Ralph Nader is responsible for billions of dollars of property damage this week, along with the deaths of dozens of people, many who were disabled or old. Ralph Nader created a proposal which limited how much insurance companies can charge. Which sounds nice on paper, but leads to California burning to the ground. It turns out that when you tell someone that they cannot raise prices, those people will frequently close up shop. Which is exactly what happened in California. Nader enacted price controls. Price controls never work; this is well understood. It's Economics 101. Nader is a dunce, and he's got people killed, numerous times.
https://en.wikipedia.org/wiki/1988_California_Proposition_103
In summary, many of these houses likely did not HAVE fire insurance. Many of these people will find themselves having to pay out-of-pocket to rebuild their homes, or they'll have to cut their losses and just move in to a rental.