“There were unburned trees and even unburned houses in the middle of burned houses.”
That caught my eye as well.
In the 1993 Laguna Beach Fire one house on a street of maybe 50 survived. It was built with fire resistance in mind.
IIRC the eaves were minimal and boxed so that superheated air wouldn’t collect under them. The attic vents were an ember-proof design. There was no exposed wood that could catch fire and lead back into the main structure.
Some of this would be very easy to incorporate into a house. Even to retrofit. California should encourage it in existing homes and require it in new construction. Insurance companies should encourage it.
Most homeowners won’t know about this construction in order to ask for it, but architects and insurers and builders should. It’s terrible to see people lose their homes and even die when a way to prevent it should be available at a reasonable cost.
Some redesign will be needed like sealing an open porch. A deck can probably be made to burn away without catching the house, but you can't keep flammable stuff under it.
One of the big challenges should be keeping dense neighborhoods safe, essentially 100% firewise compliant. California has had their day of reckoning, hopefully they can learn from it.
Japan requires earthquake building. One would think CA would have required fire resistant building a long time ago. But, no, that might upset the tree huggers and artists.