These fires are caused by arson.

The huge 2017 fire in Santa Rosa that destroyed 3000 homes started at the same time in a dozen places. That is a tell for arson.

The Carr fire in the same year, there is a video with a house literally cut in half. The left half is ashes, the right have looks as if cut by a knife and it's in perfect condition. Car wheels were literally melted off the car and yet a plastic trash bin was untouched a few feet away.

You can blame it on DEW, firebugs or terrorism. You'd be right on all counts.