The addition of the small plates came not only because they impressed Mormon, but because he was impressed that there was a greater purpose that he did not understand. We have that purpose in our Book of Mormon, for the small plates provide the beginning history of the Nephites. Mormon had written that story just as he wrote about kings Mosiah1 and Benjamin—and Mosiah2 and Alma, and so on. The beginning of Mormon’s book was lost, and the small plates provided a substitute, an alternate version, of that beginning.
Verse 9 is the transition from the discussion of the small plates into a section of Words of Mormon that bridges the short gap between the small plate history and the remaining text from Mormon’s work.