I think, one or more metal "Burrs", have stripped the insulation from some wires, causing an electrical short.
Read this:
Pulling Wire Bundles Inside Handlebars
Before running any wiring inside the new bars, take time to see if any sharp "Burrs" are there, otherwise they will quickly strip any insulation away from the wire's conductors, resulting in an electrical short.
A Dremel tool with a small stone grinding bit will smooth most burrs away. If a Dremel is not available, a small round rat tail file works just as good.
Any electrical wire splices, should be “Staggered” to avoid a lump, so the bundle will pull smoothly through the handlebar(s).
When preparing to pull the wire bundle through the bars, carefully taper the bundles end with masking tape as this makes for a better pulling situation.
I use aircraft 0.032" diameter safety wire secured to the wire bundle as a pulling medium, Nylon string or small diameter cord will work for this too.
Silicone spray or electricians pulling lubricant should be applied to the end of the wires to ease the operation. It's best to have a helper while doing this to avoid problems of possible pinched or damaged wires. Have your helper apply a steady pulling effort while you carefully feed the wire bundle into the handlebars.
After the job of pulling is done, get a multimeter, set it on the lowest ohm setting, open up the switch housings to access the wire ends and then see if a wire of two has shorted out.
Put one probe on the handlebar and the other on any soldered wire ends on the switches and see if the meter indicates continuity by either making a buzz(some meters have built in buzzers) or a display on the meter face.
An analog meter(the type with the needle indicator) will act similar (except no buzzer) by showing usually a full deflection(needle movement)if there is a short by again, checking with the lowest setting on the ohm scale of the meter.
Finding a short now is a whole lot better than when it's wired up & blowing fuses or possible stranding you on the road.....