The fuse blows because there is excessive current going through it. The current rush is between the battery and the short to ground, because ground is the opposite polarity. When a direct short to ground occurs, there is higher current between the supply positive and negative. In the context of your question, "entering the device" means going to ground. Electrons move between positive and negative. A short causes a direct path between the two, meaning less resistance, and therefore higher current, which results in a blown fuse.So it is some sort of fancy one way fuse then? If the fuse blows to stop power from exiting a device, wouldn't blowing said fuse also stop power from entering the device?