Why might a narrative nonfiction text use a narrative arc

They should serve the overall theme and subject of the story rather than being superfluous or appearing to simply pad the story. Smaller arcs may also be used for maintaining interest and tension by introducing new stakes in the conflict of the main protagonist.

Explanation:

"the sandy walls seemed to collapse in on themselves"

and

"the bloodshot waters seemed to have no bottom"

very interesting story but where is the question what is actually a question i don't understand