Coils, of whatever type, whether they be of cars or an electric motor or transformers of household electronics, can develop shorted turns. This is a short circuit across a number of loops of wire in the winding of the coil. When this occurs, it is like having an extra, and undesired, transformer secondary with a load of zero ohms resistance connected across it. This absorbs a lot of energy from the coil due to the extra current. The result is overheating, and, possibly fire or explosion such as you had.