Wow, just goes to show the power behind fire and the unpredictability of mother nature.
Now down to brass tax; What are the chances of arson vs just a natural forest fire?
I can't see any clear motives from terrorist groups, as someone mentioned previously, forest fires normally don't have any fatalities, there are many better ways to stage a terrorist attack. We have plenty of woodlands across the country, and some places do not allow people to operate chainsaws when they are in drought-level dry spells due to the possibility of sparks, so depleting lumber isn't the reason either.
As I see it, there are three possibilities. Bored kids/random arson, Natural forest fire, or false flag in order to bring more surveillance into rural area as someone touched on previously. Terrible outcome either way. I am interested however to see the aftermath on the housing market as John_Galt pointed out.