Because the Lamanites obeyed a commandment from Lehi that the Nephites weren’t obeying, namely to only have one wife, the Lord promised to bless the Lamanites. As a matter of fact, He says “The Lord God will not destroy them; and one day they shall become a blessed people” (v. 6). Why exactly? Look at verse 7. “Behold their husbands love their wives, and their wives love their husbands; and their husbands and their wives love their children.” If we followed this example of the Lamanites, would we be similarly blessed? I don’t know. But what could it possibly hurt if we tried?