How could it have been? It wasn’t like they had machine guns. In best case I believe it takes something like a full minute to reload a musket. Zerg rush would be sufficient tactics. 100 yard dash means your hoard of unarmed natives is through the musket range in maybe 10-15 seconds and pulling limbs off the spaniards already.

Why this wasn’t done is I think the big mystery and lends credence to the idea of spaniards having significant force numbers through allies.

Don't forget horses, armor, and steel weapons. It seems like Incan weapons had a lot of trouble penetrating Spanish armor, while the reverse was not true. Also, the Incas didn't just lack cavalry; they lacked the weapons and tactics to counter cavalry (such as pike formations.)

That said, I was thinking of the Battle of Cajamarca, which was actually a Spanish ambush. 100x was probably overstating it; under other circumstances (e.g. rough terrain) Spanish technology had less of an edge.