Some of my family is in affected areas. They do nightly ember watch after one nearby home saw a big one flare up.
Birds can carry burning twigs (deliberately to spread fires to flush out prey).
Arsonists.
Lightning strikes.
Electrical problems: sparks, wires rubbing on trees, faulty wires, broken wires lying on the ground, etc.
Broken glass acting as magnifying glasses.
There are plenty of reasons for wide-spread outbreaks when conditions are 'just right' over extended areas for fires.
