In short, yes. However, I would like to break apart this question to try to reformulate it to better represent the situation. It is well known and described in Conquest of America how the natives' society was formulated and run supremely by prophecies and omens. They believed solely in “omens and divinations deserving the greatest prestige” (Todorov, 66). This mindset, that all events would be justified by prophecies showed how spontaneous actions were nonexistent and that any events that occurred had to be previously seen by a sign.
I would rather change the format of the question then as these signs gave Spaniards power without them knowing. A question I propose would be the role and significance the signs played in the downfall of the nation's empire. This question puts a focus on the fall of power, rather than handing of power to the Spaniards, as well as, the idea that the Indians were solely defeated by their relentless belief in prophets. I believe that this difference is important since there was no ulterior motive for the Indians to concede their power to the Spaniards by simply following their beliefs and there were many other factors that gave enough leverage for the Spaniards to survive over the natives.
Although it is interesting to take the “control” out of defeat, yes, the Spaniards wanted to defeat the Indians, but they did not have control in it. They were going through with concepts and ideas that had never been tried in this environment before. In many ways, their societies and beliefs were so dissimilar that neither were able to overlap enough for one to have control over the other.
Signs did contribute to the downfall of the Indians, but they were not the single form of defeat by the Spaniards. The difference is that signs were the instigating factor that established differences between the two sides. Although the Spaniards, from being seen as divine gods to dictating their omens like the moon, were not aware of the impact that these signs were having in leading to a hierarchy being created. These signs allowed the Spaniards to take advantage of, and they did. For example, Columbus fabricated a tale that he would take away the moon in exchange, while he knew of the lunar eclipse, for the Indians to “bring him provisions without his having to pay for them” (Todorov, 19). This action was at the luck of Columbus that there (a) was an eclipse and (b) the Indians were easily swayed by prophecies and signs.
This truly shows how although signs were a large contributor to the downfall of the Indians, they were not the cause of defeat. It would be interesting to look at more factors that played into the complete makeup of the (Spaniards) new world.