The First Eclipse Prediction: Act of Genius, Brilliant Mistake, or Dumb Luck?
atlasobscura.com
atlasobscura.com
[1] https://en.wikipedia.org/wiki/A_Connecticut_Yankee_in_King_A...
I would expect that the Incas, and most other reasonably sophisticated cultures from that era all the way back to ancient times would know what eclipses actually are.
They were good observers of astronomical events. They would know that the Moon passed near the Sun once a month. They would know that how close that pass was varied month to month. They would know that eclipses only happen when the Moon is close to the Sun. They would see that the shape that the Sun disappears in as an eclipse progresses is circular and about the size of the Moon. All of this should tip them off to eclipses simply being the Moon passing in front of the Sun.
Furthermore, even if the motions of the Sun and Moon were too complicated for them to handle well enough to make accurate predictions, they would know that the reason they are too complicated is that they are made up of many different simple motions happening together. In other words, they would know that the motions are predictable in principle, and it is just that their mathematics is not sophisticated enough to handle the complexity.
On top of that, as a particular eclipse approaches most of the components of the Moons motion because less and less relevant. They should be able to see days before that this time the Moon is not going to miss the Sun.
Thus, I would expect the conclusion from an outsider predicting an eclipse to not be that he controls the Sun, but rather either "so what?" if the prediction is less than a couple of days before the eclipse, or "wow, you've got way better mathematics than we do!" if the prediction if the prediction is long term.
Its not the community that has this information, but a particular sect of the community, and the question how large is that section.
My expectation is not very, and was probably only known to whatever shaman classes exist (who would actually be observing it).