In fact, most don't. But they don't always end as badly as this one.
Automotive engineers have a good grasp of how to make a car safe, but once owner-installed modifications start coming into the equation, everything is out of their hands. Playing with explosive chemicals can be hugely rewarding if all goes well, but unfortunately for this fifth-generation Mustang GT this wasn't the case. Before the race started on what seems like a windy day, a small engine fire caused a nitrous line to rupture, which when combined with the high wind speed caused the car to go up in flames.
The driver and surrounding audience escaped unharmed, but the poor car was a complete loss.