[Benson]

One cause is:

"Testing" for missing engine condition by removing plug wires while engine is running instead of shorting the plug to ground will damage coils and or pickup modules.

This practice does not leave any place for high voltage to find ground so it arcs and sparks around inside the dist where it blasts the pickup module or arcs inside the coil breaking down the insulation.

First few times it might just weaken the components until finally they die.