The Incas were in the midst of a civil war over who should inherit the
throne when the Spanish arrived. With primitive weapons facing gunpowder
and armor, and a disunited military force, they presented little challenge and were quickly defeated.
The Aztecs were only recently dominant in their region, and were widely
hated for taking POWs(Prisoner of war) or demanding hostages, as these people were then
used as live human sacrifices, their beating hearts torn out and burned
on an altar, and their bodies eaten in a religious ritual. The Spanish
had little problem getting neighboring nations to help overthrow the
Aztecs.
Hope it helped :)
