When a firearrow hits an exploding crate, it imparts its linear and angular velocities to the flinders.
For the case of the firearrow, this works ok: the flinders fly off, ending up scattered around on the floor.
For the case of holding a torch next to the crate, however, the torch has no velocities, so the crate simply breaks (no explosion) and the flinders fall down to the floor.
I suggest giving random velocities to the flinders rather than taking them from the object that triggered the explosion. This should fling flinders in all directions, regardless of what the activating object was.
Things to check: how do other breakables (fractures, etc.) deal with their flinders. Breaking a window with an arrow might look better if the flinders don't fly away.
Comments?