The question of "primary" causes may itself be a subjective matter of emphasis. Which cause interests us the most? After all, there are always multiple causes. We divide them up according to our models.

I'd call nature's monstrousness the existential part of our attempt to progress (to be anomalous and unnatural, as in personal and civilized rather than animalistic and wild). And I'd think of that cause as primary, but only because I'm interested in existentialism and it's part of my philosophical worldview.

I have a number of articles on the objective sense of nature's monstrousness. It's objective, in part, because it follows from the scientific objectification of nature:

https://medium.com/grim-tidings/why-you-should-be-haunted-by-natures-physicality-4d52310d0817?sk=e1407bef36888713f080746a51b4c7ba

https://medium.com/grim-tidings/scientific-progress-as-the-ogling-and-ravaging-of-nature-cb1d1343aa3c?sk=ee62c41a69767f409d170f3b4b8cca7a

https://medium.com/grim-tidings/does-the-universe-have-a-character-89310a6534e7?sk=45b37717495e45aac297943a7fe5c834

https://medium.com/grim-tidings/the-miraculous-brute-fact-of-the-natural-order-3f877baa2c1a?sk=b4b9a733954d5e0b4ffc9cf4b2917515

https://medium.com/the-apeiron-blog/atheism-and-the-endlessness-of-explanation-22e72f89d509?source=friends_link&sk=cdc78c5a20c7678da120f27b2fbd897b