According to John Welch, in 1 Nephi 13, Nephi explained in some detail how the apostasy from early Christianity would occur. First Nephi 13:24-32 seems to identify three stages in this process--not just one.
1. This stage would have occurred simply by altering the meaning of the things taught by the Lord without necessarily changing the words themselves.
2. The Gentiles would next take away “many covenants of the Lord” (1 Nephi 13:26). We can note that this step, too could be taken without deleting any words from the Bible as such. The knowledge and benefit of the covenants of God can be lost simply by neglecting the performance of ordinances, priesthood functions, or individual covenants.
3. Nephi understood this step as a consequence of the first two, for 1 Nephi 13:28 begins with the word “wherefore.” Thus, things that were lost from the texts of the Bible were not necessarily a cause, but a result of the fact that, first, the gospel, and second, the covenants of the Lord had been lost or taken away.
Understanding this process helps us to see how the Book of Mormon corrects this situation. It contains the fulness of the gospel (see D&C 20:9). [John W. Welch, The Sermon at the Temple, and The Sermon on the Mount, pp. 88-89]