Fuses are blown when a hot goes to ground before the load.
On the circuit for the "dome", courtesy lights,the load[bulb] is hot all the time.
It turns on when the door is opened and the circuit is completed as a ground. To cause a fuse to blow, the wire that is hot between the fuse box and the bulb ,"load",has to touch metal, "ground", before the power reaches the bulb.
I hope I'm not confusing you more then helping.
Loren