Originally developed by ancient Hawaiians, surfing appeals to people due to the sport’s unusual confluence of adrenaline, skill, and high paced maneuvering, an unpredictable backdrop that is, by turns, graceful and serene, violent and formidable, and the camaraderie that often develops among people in their common quest to conquer nature.

a. surfing appeals to people due to the sport’s unusual confluence of adrenaline, skill, and high paced maneuvering, an unpredictable backdrop that is, by turns, graceful and serene, violent and formidable, and the camaraderie that often develops
b. surfing’s appeal is its unusual confluence of adrenaline, skill, and high paced maneuvering, an unpredictable backdrop that is, by turns, graceful and serene, violent and formidable, and the camaraderie that often develops

c. surfing’s appeal to people is due to the sport’s unusual confluence of adrenaline, skill, and high paced maneuvering, an unpredictable backdrop that is, by turns, graceful and serene, violent and formidable, and developing camaraderie

d. surfing appeals to people due to the sport’s unusual confluence of adrenaline, skill, and high paced maneuvering, a backdrop that is unpredictable and that is, by turns, gracefully and serenely violent and formidable, and the camaraderie that often develops

e.surfing appeals to people due to their unusual confluence of adrenaline, skill, and high paced maneuvering, an unpredictable backdrop that is, by turns, graceful and serene, violent and formidable, and the camaraderie that often develops

This sentence contains three parallel elements: “the unusual confluence,” “an unpredictable backdrop,” and “the camaraderie.” Additionally, the introductory modifying phrase “originally developed by ancient Hawaiians” correctly modifies the noun “surfing.”
(A) CORRECT. This choice properly follows rules of parallel construction and uses the introductory phrase to correctly modify the noun “surfing.”

Why are the 3 elements parallel? It looks like “the unusual confluence” and “an unpredictable backdrop” are modified nouns (adjective then noun) while camaraderie is just a noun.

Any help would be much appreciated. Thank you.

A modified noun, such as "silk shirt", is sufficiently similar to an unmodified noun, such as "jeans", to count as parallel. Thus, the following sentence is correct:

Angus wore jeans and a silk shirt.

-Jad