The reason why God destroyed Sodom and Gomorrah can be found in Christian bible in Genesis 19:4-3
Before they lay down, the men of the city, the men of Sodom, surrounded the house, both young and old, all the people from every quarter; and they called to Lot and said to him, "Where are the men who came to you tonight? Bring them out to us that we may have relations with them." But Lot went out to them at the doorway, and shut the door behind him, and said, "Please, my brothers, do not act wickedly. Now behold, I have two daughters who have not had relations with man; please let me bring them out to you, and do to them whatever you like; only do nothing to these men, inasmuch as they have come under the shelter of my roof." But they said, "Stand aside." Furthermore, they said, "This one came in as an alien, and already he is acting like a judge; now we will treat you worse than them." So they pressed hard against Lot and came near to break the door. But the men reached out their hands and brought Lot into the house with them, and shut the door. And they struck the men who were at the doorway of the house with blindness, both small and great, so that they wearied themselves trying to find the doorway.
Then the two men said to Lot, "Whom else have you here? A son-in-law, and your sons, and your daughters, and whomever you have in the city, bring them out of the place; for we are about to destroy this place, because their outcry has become so great before the Lord that the Lord has sent us to destroy it."
Biblically, one can said that God destroyed Sodom and Gomorrah because
- The Sodomites were general wickedness which had prompted the Lord to send angels to the city to investigate in the first place.
- The city was destroyed because the people of Sodom had tried to rape the angels.
- The city was destroyed because the men of Sodom had tried to engage in homosexual intercourse with the angels
- The city was destroyed for inhospitable treatment of visitors sent from the Lord.