One, stone isn't a great building material. Sure its still standing, but you wouldn't want to live in it. Second, there are tons of building regulations in the US and especially in a place like this. There isn't much that can withstand the kind of heat a forest fire makes. It isn't like the fires in a city, they are much bigger and more intense. There are several causes of this fire, one is climate change, another is not putting in the effort to clear brush. Building out of stone wouldn't have made much of a difference. The remaining structure isn't livable even if it is still standing.