God did not leave Himself without witnesses to show that He provided well to those who loved Him:
17 Nevertheless he left not himself without witness, in that he did good (Acts 14)
17 I will spare them, as a man spareth his own son that serveth him. (Malachi 3)
13 Like as a father pitieth his children, so the Lord pitieth them that fear him. (Psalms 103)
1 Run ye to and fro through the streets of Jerusalem, and see now, and know, and seek in the broad places thereof, if ye can find a man, if there be any that executeth judgment, that seeketh the truth; and I will pardon it. (Jeremiah 5)
Examples include Lot and his family who were spared, while the cities of Sodom and Gomorrah weren’t:
26 And the Lord said, If I find in Sodom fifty righteous within the city, then I will spare all the place for their sakes. (Genesis 18)
15 And when the morning arose, then the angels hastened Lot, saying, Arise, take thy wife, and thy two daughters, which are here; lest thou be consumed in the iniquity of the city. (Genesis 19)
And Noah and his family were spared, but the rest of humanity was not:
5 And spared not the old world, but saved Noah the eighth person, a preacher of righteousness, bringing in the flood upon the world of the ungodly; (2 Peter 2)
Israel was warned more than once that their capital city Jerusalem would be destroyed and its people brought into captivity if they did not follow God. Prior to the Babylonian invasion of 600 BC God warned several obedient families to flee, just like He warned Lot. The Book of Mormon is comprised of two such accounts, and a third of an exodus prior to the scattering at the time of the Tower of Babel.