Narrow, centralized elite structures are fragile and vulnerable to "outside stimuli"

From Carnage and Culture by Victor Davis Hanson. Page 217.

At the first real military engagement on the causeways on July 1, 1520, the Aztecs surrounded Cortés with the clear idea of exterminating men, not gods. Under the conditions of these nocturnal mass attacks on the narrow dikes, it was nearly impossible to capture the Castilians, and it is no accident that the vast majority of the six hundred to eight hundred or so Spaniards lost that night were deliberately killed outright or left to drown.

In the subsequent fighting during the Spanish flight to Tlaxcala, and again at the final siege of Tenochtitlán, the Mexicas employed captured Toledo blades. They may even have attempted to coerce captured conquistadors to show them the intricacies of crossbows. The Mexicas often changed their tactics, learning to avoid swarming attacks in the plains, and during the great siege showed ingenuity in confining their fighting to narrow corridors of the city, where ambushes and missile attack might nullify the Spaniards’ horses and cannon. The Aztecs eventually guessed that the Spanish were intent on their slaughter, and so logically distrusted all affirmations of Spanish mediation. They taunted their Tlaxcalan enemies with prescient boasts that after their own demise, they, too, would end up as slaves to the Spanish.

If the Aztecs fought with any disadvantage, it was one of training and custom that had taught them to capture and bind rather than slice apart an adversary—habits that would prove hard to shake even against killers like the Spanish, who gave no quarter. Still, we must remember that the notion that soldiers should seek to capture rather than kill their enemy is a most un-Western one, and only reaffirms our general thesis that the entire menu of Western warfare—its tactics of annihilation, mass assault, disciplined files and ranks, and superior technology—was largely responsible for the conquest of Mexico.

Besides the overriding problem of inferior weaponry and tactics, the greatest cultural disadvantage of the Aztecs has often gone unnoticed: that of the age-old problem of systems collapse that threatens all palatial dynasties in which political power is concentrated among a tiny elite— another non-European phenomenon that has given Western armies enormous advantages in cross-cultural collisions. The abrupt destruction of the Mycenaean palaces (ca. 1200 B.C.), the sudden disintegration of the Persian Empire with Darius III’s flight at Gaugamela, the end of the Incas, and the rapid collapse of the Soviet Union all attest that the way of palatial dynasties is one of extreme precariousness to outside stimuli. Anytime a narrow elite seeks to control all economic and political activity from a fortified citadel, island redoubt, grand palace, or walled Kremlin, the unraveling of empire shortly follows the demise, flight, or discrediting of such imperial grandees—again in contrast to more decentralized, less stratified, and locally controlled Western political and economic entities. Cortés himself sensed that vulnerability and thus kidnapped Montezuma within a week of arrival. With the final flight of the successor emperor Cuauhtémoc in August 1521 the final resistance of the Aztecs came abruptly to an end.