Another possibility is that the animal bodies floated into the lake or were washed there by flooding. The researchers ruled these scenarios out, because the structure of the sediments and the intactness of the animal skeletons didn’t fit with these explanations.
Well... if they were buried in ash, they could easily be intact. It’s ash.
If they were washed there by flooding, I have serious doubts that they would be ‘intact’. Those guys chasing Moses and their chariots didn’t make it ‘intact’.