The Mesoamerican civilization had reached the high level of development before the arrival of European colonists. However, their level of development was still lower compared to that of Spaniards and some civilizations, such as Mayan city-states were in decline at the time of the arrival of conquistadors. In addition, internal conflicts provoked the failure of the Mesoamerican civilization to resist to the Spanish conquest. In such a way, in spite the tremendous progress and achievements of the Mesoamerican civilization, it had failed to resist to the Spanish conquest and fell under the first strikes of European colonists.
In fact, by the time of the first encounter of Spaniards and Native Americans in Mesoamerica, there was only one major power in the region, the Aztecs Empire. The Aztecs became the dominant tribe in Mexico and Central America due to aggressive military policy. They conquered neighboring tribes and forced them to pay tribute which accumulated the wealth of Aztecs but their power and domination in the region was grounded on their military power. Therefore, the defeat of the Aztecs army would ruin their empire. Other civilizations of Mesoamerica, such as that of Olmecs and Mayas had disappeared by the time of the Spanish conquest and their glory and power was in the more or less distant past.
In such a situation, Aztecs was the only power that could resist to the Spanish conquest. By the time of the encounter, Aztecs had well-developed social hierarchy, topped by the monarch and his noblemen and priesthood. Aztecs developed their art, religion and culture incorporating religious and cultural traditions of conquered tribes. They were the leading military and political power in the region, while tributes other tribes had to pay them made them economically stronger than any other tribe in the region.
On the other hand, the superiority of Aztecs over neighboring tribes annihilated in face of Spaniards, who were much more superior compared to Aztecs in terms of technology, military equipment and tactics, and strategy. In fact, Aztecs had no fire arms, while their armor was absolutely ineffective in face of Spanish weapon. At the same time, the Spanish armor protected Spaniards from the weapon which was deadly for local tribes. This is why, when Aztecs saw that Spaniards cannot be killed they grew superstitious about the divine origin of Spaniards. At this point, the myth about the arrival of gods from the East played a trick on Aztecs because they treated Spaniards as messengers of gods or gods proper. In addition, Spaniards surprised Aztecs, because they had things which Aztecs had never seen before. For instance, Aztecs had never seen horses, which were common for Spaniards.
Along with supernatural fear, Aztecs could not confront the military order, strategy and tactics of Spaniards, who could deceive and defeat Aztecs easily and so they did in the conquest of Aztecs and their capital, Tenochtitlan. In addition, other tribes did not support Aztecs in the struggle against Spaniards. In stark contrast, they welcomed the defeat of Aztecs because their defeat liberated them from tribute they had to pay Aztecs on the regular basis.
Thus, the technological and military superiority, superstitions and myths of Aztecs, and the lack of support from the part of other tribes contributed to the defeat of Aztecs as the major power in Mesoamerica in the struggle against the Spanish conquest.