I'd be surprised if this was caused by transient spike. Looks more like a wire got pinched on the box. If it was a spike I'd think that MOV between the hot and neutral would appear more damaged.

That little red disc between the white and the black is a surge arrestor. It's a Metal oxide varistor and its job is to act like a dead short if high voltages are present. They are kind of the sacrificial lamb that throws itself in front of the spike, protecting everything downstream. When they get hit by lightening they usually are badly discolored and even split open. A pinched wire in the power box could go undetected for a long time. One good game with lots of nudging could have caused it to short out and fry.

Not all surge supression is created equally. At $17 you likely bought a glorified power bar.
Also not all transient spikes are lightning related. I just finished replacing a 500HP motor and VFD that were damaged due to a transient spike from a car hittimg a power pole, total costs so far $135k
If you're really concerned with a spike you should consider whole house protection which is a surge suppresion unit that connects to the electrical panel, they run about $180 (cdn), but even those won't help if your house is hit by lighting. I've had to do an investigation on a house that took a direct hit and it was amazing how destructive it is. Fires at multiple points in the house, some electronics melted, some not effected at all and a ladscaping railroad tie was thrown across the yard and thrpugh the neighbour's sliding glass windows... No amount of surge suppresion is going to be able to dissipate that kind of energy.