Our system can't distinguish between an increase in request for electricity caused by a break in the line or because many people in one area are coming home from work and turning on their electrical appliances. If this doesn't happen because the wire has fallen on a poor conductor, our line will remain energized. When a live wire falls, it makes sparks. A power line sparks if it falls to the ground and does not make firm contact with the ground or other material. When a wire falls to the ground and makes firm contact, it will often make no noise or sparks, and will give the impression of being de-energized.
Wood is an insulator.
Wood is in fact a conductor, though not a good one. But the higher the voltage, the easier it is for electricity to move through wood. And if the wood is damp, it changes the equation and wood becomes a good conductor, even at low voltage. So be careful standing on a wooden crate to turn on your main fuse box or when you use a wooden ladder. Household rubber gloves or rubber soled shoes insulate.