It was a mechanical switch??..was there an inductive load?
However...without an inductive load, I'm wondering if the current can be high enough for "lift off" contact heating.. Does the last little bit of metal contact that breaks away .the I^2R power makes an arc spot? But wouldn't the arc be a mini explosion and it blows the contact further away???. A good thing.
Similiarly, I think power mosfets can blow up if the turn off transition power is too high.. (no inductive load). That's a good thing for a breaker.. The power mosfet can act like an active fuse that burns out or blows up.
D from BC