The original text did not have the clause “and it fell”. Scribe 3 of 𝓞 never wrote it into the text as he took down Joseph Smith’s dictation. But at some later period, Oliver Cowdery supralinearly inserted this clause in 𝓞. This extra clause was copied into 𝓟 and has been included in every printed edition. Undoubtedly, the linguistic source for the clause is from the Sermon on the Mount where Jesus refers to the fall of the house built by the foolish man:
The similarity of the Book of Mormon’s “and the fall thereof was exceeding great” with the King James Bible’s “and great was the fall of it” seems to have triggered Oliver’s desire to add the explanatory (but unnecessary) “and it fell”.
In two other passages, the text refers to the fall of the great and abominable church. In these instances, the preceding language refers to this church tumbling down, which we readily interpret as its fall:
In both examples, the last clause parallels the King James Bible’s “and great was the fall of it”, yet in both cases there is no directly parallel clause “and it fell”.
We should note that the last clause in 1 Nephi 11:36 (“and the fall thereof was exceeding great”) is not as close to the biblical parallel as the two other Book of Mormon passages are (1 Nephi 22:14 and 2 Nephi 28:18). Further, since “the fall thereof ” in 1 Nephi 11:36 comes at the beginning of the clause, this noun phrase can be considered a new topic for which no preceding explanation is necessary. In the Matthew passage and the two other Book of Mormon passages, the predicate adjective great occurs first and the subject noun phrase the fall comes later in the clause (after the verb). Such an inverted word order is acceptable because the fall has already been referred to (directly in Matthew 7:27 and indirectly in 1 Nephi 22:14 and 2 Nephi 28:18). There is no need in 1 Nephi 11:36 for Oliver Cowdery’s explanatory “and it fell”, and it should therefore be removed.
Summary: Restore the original text for 1 Nephi 11:36 (that is, without the clause “and it fell”); this textual addition apparently represents a borrowing from Matthew 7:27, yet the word order in 1 Nephi 11:36 implies that this added clause is unnecessary.