The Book of Mormon prophecy of Jerusalem being destroyed seemed entirely conditional and the city would be spared upon conditions of repentance. The survival of the city seems to hinge on one word,
"must", which implies that the destruction of the city was entirely based on whether the Jews repent or not.
they must repent, or the great city of Jerusalem must be destroyed.
Based on the story of Lehi and his family in the wilderness followed by their perilous journey across the great deep, it seems that Laman and Lemuel were not true-blue believers and were constantly rebelling against Lehi and the more faithful son, Nephi. This being the case, it seems difficult to believe that the rebellious sons actually believed in the silly prophecies of their visionary father. Isn't that right? The sons were more interested in his property and maintaining wealth and status in Jerusalem. Doesn't the Book of Mormon adequately express the lack of faith and belief of Laman and Lemuel? That being the case, they would not have seen repentance as being a condition in which Jerusalem would be spared from foreign destruction. If they don't believe in the Lord and his mandate to repent according to visionary prophets then why would they think that the Lord could spare them? Based on the story in the Book of Mormon, reading between the lines, Laman and Lemuel weren't real believers but went along with Lehi because they really had no choice seeing he was the father of the estate and was not about to leave it into their hands and take off with just Sam and Nephi. So the story relents by dragging the unbelieving sons along.
Thus, the unbelieving sons never believed their idiot father but go along for the ride because they have no choice. And if they don't believe in the idiot dreams and prophecies of their father then they don't believe that the LORD is going to save Jerusalem from foreign invasion. So it would be like old times all over again and Laman and Lemuel could easily imagine Jerusalem getting sacked (destroyed) and the place being totally subjugated by foreign powers. Therefore, the Book of Mormon narrative about the older sons not believing that the great city Jerusalem could be destroyed is inconsistent with their beliefs and faith in the prophecy and contradicts previous historical accounts whereby Jerusalem succumbed.
When the Book of Mormon says that Laman and Lemuel
"did not believe that Jerusalem, that great city, could be destroyed", it's the same as saying that Laman and Lemuel were of great faith and mightily believed in the prophecy and dreams of their father whereby Jerusalem could be spared on account of their faith and repentance. But according to the story, the older sons were not men of faith and hardly wanted to repent. So, it makes no sense that they believe Jerusalem could not fall because the LORD in whom they cared less was going to save them.
Does that help, a little, Mig190 ?
Thanks for sharing your historical context.