Seems everyone has a grasp on Ohm's Law but it isn't really a matter of upsetting the triangle but it's a matter of current surges. A fuse is basically a filament in a glass tube. The filament is designed to part if it gets too hot. Under normal conditions, there is a small amount of resistance in the fuse thus a very small amount of voltage drop across the fuse. So, as current flows through the fuse, the filament heats up just like a light bulb filament does. When the current is removed, the filament cools down. This cycle weakens the filament over time. Because of this, the fuse has a limited life span, just like a light bulb. Now, put a loose connection in the cabling between the source and the load, whether before the fuse or after, and as that loose connection moves and increases and decreases the resistance in the circuit it also increases and decreases the current flowing in that circuit. Depending on what kind of load (and the corresponding amount of current flowing) in that circuit, this cycling of the heating of that filament can cause quick failure. It's like standing there turning a light on and off constantly. That light is going to fail sooner than later. The more extreme the current surge either due to the low rating of the fuse (thinner filament) or the high current draw of the load the faster the fuse will fail.
And usually at the worst possible moment.
