Wildfire risk comes from 1) vast amounts of highly vulnerable and flammable vegetation and 2) blown embers.

The fire front isn't leaping house to house. It's being blown, often miles, by fierce, fire-driven and -generated, winds.

This is a demonstration of ember-driven ignition:

https://youtube.com/watch?v=_Vh4cQdH26g

And the phenomenon in the Paradise / Camp Fire:

https://youtube.com/watch?v=gxt7L4x_NQo&t=350