When Alma is instructing his son Helaman concerning his charge over the records, he notes specifically that the plates of Ether should be preserved so that their works of darkness might be made known (Alma 37:21). As Moroni unfolds the story of the Jaredites from Ether’s record, the “secret plans of wickedness” are the recurring theme that underlies the political destructions of the people.
Moroni is using the information from the plates of Ether for precisely the purpose of exposing those secret works. The exposure is not of the content of the works, for Moroni specifically avoids that (Ether 8:20). However, he exposes the results of the secret works. That result was the destruction of the Jaredites, and later the destruction of the Nephites (Ether 8:21). This great final war that proves the destruction of the Jaredites begins with secret combinations.