He made a poor choice, which put him too close to the evil influence of Sodom. Since he selfishly chose the well watered plains of Jordan for himself, God was choosing the promised land for Abram.
'Now Abram dwelt in the promised land of Canaan West of the Jordan River, and Lot dwelt in the cities of the plain, and pitched his tent towards Sodom' (Gen. 13:11-12). Look at the pitiful life of Lot, as he pitched his tent toward Sodom. First, Lot lifted up his eyes and beheld. Second, he 'chose him all the plain of Jordan.' Third, he 'separated' himself from Abram. Fourth, he 'dwelt in the cities of the plain.' Fifth, he 'pitched his tent toward Sodom.' Sixth, he 'dwelt in Sodom' (Gen.14:12). Last, but not least, he sat in the gate of Sodom and let his daughters marry the men of Sodom (Gen 19:1, 14). Did you ever hear the saying 'Behold how great a fire a little matter kindleth?' Sin is a cancer. It starts out small, but once you start sinning, it just keeps spreading.
Another example was the Apostle Peter. Look at how he fell further into sin, on the occasion that he denied the Lord. Remember his boasting 'Though all shall be offended, yet not will I' Mark 14:29). Then, in the garden of Gethesmane when he should have been watching and praying, he was sleeping (Mark 14:37)! Remember when he was seated at the fire, when he was cursing and denying that he even knew the Lord (Matt. 26:69)!
Whenever we are in a sinful situation, the Lord will give us a warning, because he is merciful towards us. In Genesis, Chapter 14, Lot was captured in the battle with the four kings and lost his property. If it wasn't for his uncle Abram and his servants, he probably would have been killed. But he still associated with the world system, because he went back to Sodom. His heart still wasn't changed.
In Genesis, Chapter 18, the Lord Jesus Christ himself in theophanic manifestation, made known to Abraham (as his name has now been changed) what he is about to do, but didn't reveal anything to Lot, because Lot had sunk so low morally, he was not in communication with God. The secret of the Lord is with them that fear him. There were two angels who accompanied the Lord to Abraham's tent, but left to go to Sodom. Abraham was interceding with the Lord, who stayed behind. Look at the contrasts between Abraham and Lot. In Genesis 18, the Lord and the angels fellowshipped in Abraham's tent, whereas in Genesis 19, they refused to go into Lot's house but were going to abide in the street'. Also, it was in the heat of the day (Gen. 18:1) that they visited Abraham; whereas, it was in the evening (Gen. 19:1) that they appeared to Lot. Then notice how low he sunk morally when he offered his daughters to the men of Sodom to save himself (Gen 19:8). Notice how his testimony had no power when he warned his sons-in-law of the coming doom of Sodom. They laughed at him. He dragged his feet, because he was so attached to Sodom that the angels had to physically grab him and drag him out of the city.