Smoked HEI coil

Can someone confirm how I did this?
I've managed to smoke two HEI coils. It's in a race car, so there's minimal wiring, but in both cases the car has sat with the ignition on
and the car not running while I worked on other stuff. (it got left on by accident for over an hour.) Eventually the coil gets HOT - I melted one bad enough it actually melted a hole in the cap.
I have three switches in the Camaro - one for main power, one for ignition (coil) and one for the starter. The ignition and starter are only live if the main switch is on.
I wrote the first one off as shorted from race damage, but the second one happened yesterday while I was working on a fan shroud - am I shorting something out????
I don't quite know how to explain it, but is it because the coil is energized it generates heat and doesn't ever discharge? I really don't know what's the deal here... but that's two coils that were hot as heck...
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