Why God Rained Fire on Sodom and Gomorrah
Genesis 19:24–25 identifies the agent, the means and the completeness of Sodom's destruction: Yahweh himself rained fire from the sky and overthrew the cities and everything in the plain. The reason lies in the surrounding narrative, not in these two verses alone.
Why God Destroyed Sodom and Gomorrah
Genesis 19 answers the question by tying the destruction to a great outcry against Sodom's flagrant wickedness, shown in the mob at Lot's door. The same chapter shows God pulling Lot and his family out by the hand.