There are two things that make electricians worry; fire and electrical shock. The National Electric Code is written around these two dangers.
One old timer electrician told me that it was very difficult to start a fire with electricity. All combinations had to be just right. To start any fire, conditions have to be just right. For instance, try starting a campfire with damp wood.
Electrical fires do happen. There are trained fire investigators who can get into a burned area and determine how, why, and where a fire started. When electricity is the root cause, the NEC is adjusted to meet experience.
I have worked on a number of jobs after the fire was out. Insulation really does make a difference. Many times I have seen Romex (NMB) wire cable, with all of the wrapping burned off. But where the Romex enters the insulation, the wire is in very good shape.
Making electrical repairs in such an instance, I can put in a junction box and pick up the undamaged wire in the insulation. Thereafter I can finish the circuit with new wire.
One particular job I recall necessitated replacing almost all the wiring in the building. I worried a lot about the area where I couldn’t get to the wiring. After 30 years the building is still standing, so I have decided to quit worrying.
In one apartment that had burned (1 unit out of 10), the manager wanted the power turned back on before the walls and ceiling were repaired. I devised a way to re-wire the place and leave the wall building to later, thus providing power to the area before the carpenters “renovated” the fire damage.
It must have worked, because I got paid and no one called to complain about anything.
Back in the ‘90s there was a firestorm created by outdoor, high voltage electrical wires. It took a combination of high winds and trees that came down on high voltage power lines. The fire spread for miles.
We wired a number of new buildings that replaced the ones that had been destroyed.