It looks like the author wanted to understand the meaning of 美丽 in this context but failed so instead he/she just dumped all his raw research and personal opinions without justifications and deeper analysis.
> Note that, as a rhetorical progression, the five modifiers from "rich and powerful" to "beautiful" become increasingly abstract, with "beautiful" amounting to an unassailable purified truth.
This sentence is not really making sense to me. The 5 adjectives are all abstract, and 美丽 is the less abstract one among them because you normally use it to refer to physically objects.
Also, the discussion on single character vs two characters are pretty much irrelevant to the contextual meaning of the word 美丽 here, because the two character word is used just to make all 5 adjectives have two characters uniformly (more beautiful). If the other 4 adjectives were single character, this word would also be single character. In Chinese, the usage of single vs multiple characters is mostly purely for aesthetics of the written sentence. For example:
真，善，美 (all single characters, looks and sounds nice)
vs
美丽的上海 (adjective and subject are both two characters, looks and sounds nice)