Heat alone doesn't do much to carbon. It can get yellow hot without destruction.
What do you call "explode"? And how much current do you use: 100A? 10kA? Do you see sparks?
I could imagine that the electrolyte vaporizes brutally where the electrode touches it, and the bubble's pressure breaks the electrode. Or better, the sparks (if any) erode the electrodes.
Less obvious things happen with graphite, for instance soaking hydrogen over time. Back to normal state might release energy.