Why would clipping a wire cause a bomb to explode?
I suspect that there is an ISO standard that bomb makers follow.  As evidence of this is the fact that in about 50% of the movies, there is a statement like "remember to clip the red wire and NOT the blue" or some similar statement. SO I suspect that embedded in the ISO document is a standard that indicates the standards for booby-trapping and which wires cause the bomb to explode and which cause the bomb to fail.