88 Coil fried. What caused that?
 

My 88 died again. After having it towed home I figured out that the coil was fried. The red (12 volt) lead going into the coil was melted and the casing around the coil was all charred. I recently replaced the coil in one of my throwing parts at the car fits. The old one was not bad but I replaced it with a cheap $15 coil from AutoZone. My questions are these:

Did I have a cheap or defective coil that just gave out?
If so, what coil should I get?
Could something else have caused this to happen?The power lead that connects to the coil reads the normal 12V.

I got a replacement from AutoZone but I'm afraid of having the same issue again. The cost of getting a tow would go a long way toward buying a better coil.