You're missing the lead in. God is visiting Abraham and says he'll destroy Sodom and Gommorah because the poor have been crying out against it. Abraham goes "oh crap, my nephew(maybe cousin? I forgor) lives there. Maybe spare them?" God says if he finds 100 good people they're spared. Abraham bargains him down slowly to 10. The angels are looking for just 10 good people, but they're all so wicked they see someone who doesn't have family nearby to protect them and immediately want to gangrape them. Lot offers his daughters because quests are very important in this time, daughters are not. She gets turned to salt because you don't disobey God. SHe couldn't give up her old life in a sense, and had to see the sinful world she was leaving behind.