Ancient people used their brains differently than we do. We rely on books, programs, and aids (e.g. scripture apps with search functions) whereas many ancient people had most of the scriptures committed to memory. When Benjamin said, "Remember, remember, O man," he meant, "Remember my words; memorize them." I know that it was not so long ago that Joseph Smith and the boys, when they rode from Kirtland to Missouri, would memorize and recite scriptures and many of them could recite the whole New Testament as a result. It was not long ago that entrance to some Islamic universities required applicants to know the whole Quran from memory. In the 18th century, entrance to colleges like Harvard and Yale required students to be able to sight-read and translate Greek and Latin classic. For years, Jewish boys were expected to know the Talmud by heart for their Bar Mitzvah. That is what the human brain is capable of.
In the year 2000, I was teaching an honors BYU Book of Mormon class, and for the last six weeks of the semester we were studying King Benjamin. The requirement was for them to memorize the entire speech. I had them perform it in groups where they could do it like a Greek chorus, but I also assigned them to do certain parts by themselves. It is possible to recite this whole talk in 35 minutes. Eleven years later, I still got reports from the students that it was the best thing they did at BYU.
Steven L. Olsen, "Memory and Identity in the Book of Mormon," Journal of the Book of Mormon and Other Restoration Scripture 22, no. 2 (2013): 40–51.
Louis Midgley, "The Ways of Remembrance," in Rediscovering the Book of Mormon: Insights You May Have Missed Before, ed. John L. Sorenson and Melvin J. Thorne (Salt Lake City and Provo, UT: Deseret Book and FARMS, 1991), 168–176.
Louis Midgley, "’O Man, Remember, and Perish Not’ (Mosiah 4:30)," in Reexploring the Book of Mormon: A Decade of New Research, ed. John W. Welch (Salt Lake City and Provo, UT: Deseret Book and FARMS, 1992), 127–129.