How did divisions in within the aztec and incan empires the spanish?

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 :)