I guess I've been lucky (which I've just jinxed). But I've replaced bars and grips without putting in the shim, extended wires, replaced rear fender
and have never had a problem. I'm glad you figured it out. Question is WHY'D the fuse blow? Now THAT would make Me lose sleep.
And no one thinks your an idiot. Well most people don't, I'm sure there are a few.

 

As others have said, you might have broke the front brake light switch since you didn't shim the brake lever when you took the switch controls off. Can't tell you how many times I've seen this. If the switch isn't broke where it contacts the lever, make sure the little plunger moves in/out freely. It might be jammed.

 

There is also a folded copper shim on the back side of the brake switch, usually there is clear RTV silicone over it inside of the switch housing, it keeps the switch out to make contact with the brake lever.