Would not surprise me if all these fires were the work of terrorists.
When humidity is down near 5% in lots of beetle kill pines, just about anything that emits a spark or glow—no matter how tiny—can start a wildfire. Lightning, generator exhausts or chimney flues without spark arrestors, a bullet hitting a grassy spot, a spark from a cookout,...
And before anyone goes crazy on “a bullet hitting a grassy spot,” I was in the Guard and put out a few fires on ranges.
And BTW, I lived near quite a few wildfires. There were almost always assumptions and rumors about arson and homeless people, but most of the fires near me were started by lightning (not many people around). Many others were accidents involving established residents with controlled burns (with permits), campfires, smoking, cooking out, machines emitting sparks and the like. The only fire that I remember involving arson was the Hayman Fire, started by a government employee who was hating on her ex.
In California? I don’t know. The population per square mile is huge there, with many people of different cultures.