Both fuses become common as splice S121, just below the right side headlight box on the diagram. If the wire heading South, after both fuses, after both headlights, touched ground, BLAM and the smoke gets out of the fuses. Or spppttt if you prefer, more silent.
If the headlight switch was in 2 or 3, Low or High beam, rather than OFF, power could flow through the switch to ground. It is possible that enough could flow through two fuses simultaneously to cook the headlight switch(melt the internals). I do not know how much fun it would be to check the switch make/break connections as shown in the diagram, but a smoked switch could prevent headlight operation.