Here are the first few things that come to mind:

1) Those crimp connectors are not the way to make a quality connection but they should handle moderate loads.
2) You used too small of a wire for the load. Remember that all the instrument lights are also carried on the driving light circuit.
3) You failed to use relays to carry the load stated above.
4) There was a short somewhere in the system.
5) You failed to use the proper size fuse in the circuit.