Why did an Atheist cause "Wildfire" in Australia ? Only an Atheist could do such a thing..?

I'm not an atheist, but I think your question contains a ridiculous umption. Not all atheists are pyromaniacs, and not all religious people are whiter than white. Clearly, whoever did it is very sick as no rational human could have done such a terrible thing. It could have been a religious fanatic, an atheist or just about anyone with a grudge of some sort or a mental problem.