Final answer:
Montezuma may have believed Cortes to be Quetzalcoatl due to prophecies that a white-skinned god would return, which, paired with the advanced technology and appearance of the Spanish, seemed to fulfill the Aztec religious predictions and interpreted omens.
Step-by-step explanation:
Montezuma believed that Cortes was the god Quetzalcoatl likely due to a combination of factors, including prophecies, misconceptions due to advanced technology, and the physical appearance of the Spaniards which matched the legendary descriptions of Quetzalcoatl as a white-skinned god. The Aztec religious beliefs at the time were steeped in prophecies that foretold the return of Quetzalcoatl. These beliefs were intensified by Cortés' fortuitous timing, arriving in a period following various omens that Moctezuma could not explain, such as a fiery object in the sky and the wailing of a woman. Historians suggest that Moctezuma may have interpreted these signs along with the appearance of the Spanish as fulfillment of these prophecies.
Furthermore, the Aztecs had never seen horses, and the sight of the conquistadors riding them may have created an impression of a singular, divine creature, as described by Bernal Díaz. The mythology surrounding Quetzalcoatl and its connection to the events of the conquest relies on sources contemporary with the Conquest of the Aztec Empire, reinforcing the historical context of this belief.