This area sits in a cold-moderate climate band, and cable failure here tracks with that. Galvanized cable holds up fine against humidity, but repeated freeze-thaw cycles through a Tennessee winter work rust into the strands faster at the point where the cable bends around the drum and the bottom bracket - the two spots that flex every single cycle the door runs. On a door built in the early 1990s, that's three decades of freeze-thaw cycling on the same two bend points, which is exactly where we find the failures.
It's not a dramatic cause. It's just the slow kind of wear nobody notices until the cable lets go.