From my memory and bits and pieces of what I read from different sources:

The camp was in a flood zone. The flood map had been altered, removing some of the buildings from the flood area.

The NWS did issue warnings in enough time for evacuation. The problem was that those who needed to be aware of those warnings, were not. There were no warning sirens that could have been sounded (the system was too expensive to install). Cell reception in the area was spotty.

I am sure there is more to the story - I am not that well informed on it. And of course, there is fingering point galore going on.

It's so very tragic.