Lehi and the family of Ishmael left Jerusalem before its destruction. In 1 Nephi 7:7, Laman and Lemuel and some of Ishmael’s family wanted to go back to Jerusalem. Its destruction, as Lehi had prophesied, was not yet certain. But Nephi also was allowed to see the things that his father had seen (1 Nephi 11:1; 14:29), which may have included what Lehi read in the heavenly judgment book (1 Nephi 1), as well as Lehi’s dream (1 Nephi 8). Before leaving the Old World, Nephi subdued his brothers, assuring them that the people in Jerusalem were wicked and were "at this day about to be destroyed … save only a few, who shall be led away into captivity" (1 Nephi 17:43). Having arrived at the new land of promise, Lehi now confirmed that he had "seen a vision, in which I know that Jerusalem is destroyed; and had we remained in Jerusalem we should also have perished" (2 Nephi 1:4).The Lord blessed Lehi with a knowledge that Jerusalem had been destroyed, confirming Lehi’s prophecies in yet another vision. We know from various historical sources that Jerusalem was destroyed sometime between 590 BC and 586 BC by the Babylonians.
Lehi’s prophecy in this regard was historically confirmed in Nephite history about 400 years later. In Omni 1:15, Mosiah learned that the people of Zarahemla came out from Jerusalem at the time that Zedekiah, King of Judah, was carried away captive into Babylon. One of Zedekiah’s sons, Mulek, escaped the Babylonian captivity and with a group of people left Jerusalem, crossed the ocean, and came to the western hemisphere. They were the people of Zarahemla, and their ancestors had witnessed the destruction of Jerusalem.
Book of Mormon Central, "Why Should Readers Pay Close Attention to the Mulekites? (Omni 1:19)," KnoWhy 434 (May 17, 2018). "Mulek’s witness of Jerusalem’s destruction proved that Lehi and Nephi were true prophets and, therefore, that Laman and Lemuel had unjustly rebelled against them."