Large fires can be started by quite hard to prevent things. We had a fire a couple of years ago that burned a bunch of houses that was started by a lightning strike on a single tree a week or more beforehand. The fire smoldered unnoticed near a popular hiking trail, inside the trunk then emerged much later when wind speed became high.

In current nature this can be blamed on incorrect maintenance or zoning and even education, not just the one who brings the spark.