@freemo It was such an unexpected development. The CFCs were amazing in terms of stability, safety and utility. Finally something that isn't going to go boom, not cause severe reactions and be an excellent solvent among other things.

Turns out that UV Radiation made it eat away at the layer in a remarkable way. That's the story I remember. I don't know how much UV radiation that altitude would typically see but the conversion of Oxygen to Ozone requires a fair amount of energy.