The entire story rests on a relatively small number of artifacts.
I’m not going to engage in speculation, but will simply say that these artifacts are thus far consistent with the theory of civilization developed by Ibn Khaldun. That there is a cycle to civilization. An initial period of ascent, characterized by the flourishing of the economy, of the arts and of sciences, and of military might, when larger and larger revenues are generated from low taxes. Then, a period of decline, characterized by corruption, when smaller revenues are generated from increasing high taxes.
Here is what we know: all throughout the world, wherever there have been men, there is evidence of civilization. In many places, cities and such have been discovered, their associated civilization only known through artifacts. In some other places, we have actual histories that involve the waxing and waning of civilization.
To me, what the sum of this does is affirm my belief that “all men are created,” as we say in our Declaration of Independence. It also speaks to the fragile nature of civilization and that power corrupts.
The fire and the human sacrifice seem to suggest that like the Azetecs, the Cahokians had many enemies. Success made them soft and at some point one or more of their enemies ganged up on them and burned down their civilization.