Genesis 19:18-21 meaning

Lot proposes another idea in the midst of destruction, "I cannot escape to the mountains, for the disaster will overtake me and I will die." Lot argues that it was impossible to make it to the mountains before the disaster strikes. Lot recognizes the favor God has shown by saving his life. He argues for a town close by. But his argument could have more to do with living in a town than in escaping disaster. Even though his righteous soul was vexed in Sodom, we saw that he had become quite intimate with city life.  Therefore, he proposes taking sanctuary in the small nearby town of Zoar. 

Although Lot is grateful God will save him from the destruction, he bargained for a better landing spot than the mountains saying, "This town is near enough to flee to…please, let me escape there."  This small city was scheduled for annihilation too. Lot was suggesting that Zoar was small and insignificant. Surely this little town could be spared that his life may be saved.

A further indication of God's mercy in the context of the extensive judgment God grants Lot this request also, not to overthrow the town. Zoar was a member of the wicked cities, but it was spared because of Lot. The town will be spared, but we will see that it will end up as a snare to Lot, and he will end up in the mountains anyway.