Didn’t DeSoto report of massive Mississippian populations and villages in his travels? And 200 years later the early French Explorers found nothing.
One theory was that the herds of swine that DeSoto brought with him infected the native deer population killing them to the point of near extinction in that part of the country.
Consequently the indigenous population starved.
Yes... Cahokia had already risen and fallen by DeSoto’s time, though other Mississippian fiefdoms continued without it.