It is sad.
We have known how to build fireproof buldings for decades.
Instead, in areas we know are prone to wildfires, we build homes which are vulnerable to fires.
If I had his money, I would have elected for a stone exterior above ground; steel shutters made to easily cover the windows without outside manpower; Steel roof structure with steel beams and steel exterior roofing. The bottom four feet of the ground floor would be earth sheltered. Add significant interior, fire resistant insulation. There would be a fire system to supply the roof with water to cool it during a fire, by running down from the peak, and a drainage system to direct the water away from the house.
Those things do not add much to the cost of a mansion when built in. The make the house very hard to burn down, and esy to heat and cool. They are a good way toward fallout protection.
Nothing is fireproof. You can make it highly resistant, but if your landscaping looks like the entrance to the bat cave or a structure close to the house burns there’s a fair chance it will burn.
Everything in my shipping container 30 feet from the burning structure burned my propane tanks 75 feet from a burning structure cooked off.
My cousins lived in fire prone mountains in northern California and they had a swimming pool.
They had a gas electric generator and a large submersible water pump attached to sprinkler system that could drench the entire house.
If there was a fire threat they would fire up the generator and evacuate. The system could run by its self for 12 hours or until it ran out of gas.
The system cost less than a thousand bucks.