I am not sure of the newer model trail cameras, but the old ones as well as the home built I was familar with, shorting them out would not cause an explosion. The wires would just burn out or the boards would fry. Now BATTERIES can cause this as well as the Flash. Flash cameras work with COMPASITORS which store energy, enough energy to light a bright flash at an instant when triggered. If you have worked on a trail camera and have touched one of these, you will know how much energy they store.

Believe me, more then a few cameras have crossed the room unexpectedly out of someones hands after an accidental touch.
Tiny ants have also been know to cause major trouble like this. They cut holes (tiny hardly visable) in rubber boots that cover switches, plugs ect and then go into the box and eat the wiring and cause trouble.
I could not tell, but the battery did not look like it over heated and exploded, but that would cause that dammage.