Final answer:
Montezuma's mistake was not taking immediate action against Hernan Cortes and his men, which allowed the Spanish conquistadors to gain a foothold in Tenochtitlan and ultimately conquer the Aztec empire.
Step-by-step explanation:
One mistake made by Montezuma was not taking immediate action against Hernan Cortes and his Spanish conquistadors when they first arrived in Tenochtitlan.
This mistake was significant because it gave Cortes and his men time to establish a presence in the city, win allies among Montezuma's enemies, and gain access to valuable resources.
Instead of taking decisive action, Montezuma initially welcomed Cortes as a guest, which allowed the Spanish to gain a strategic advantage and eventually conquer the Aztec empire.
Learn more about Montezuma's mistake in dealing with Hernan Cortes and the Spanish conquistadors