Lot had lived in Sodom somewhere between 14 and 24 years. Long enough to have two daughters born there who had somehow picked up the defiled mentality of the culture there, and brought it with them into the cave.
And the dynamic of Lot’s family devolved from walking with the L-rd righteously to one of fear and self-preservation.
P.S: To people who like to read the Bible with a critical eye and say, “this isn’t the Word of G-d. Just look at their behavior. This isn’t ethical. G-d and these people are monsters.”:
1) Just because the Bible says something took place doesn’t mean the Bible gives tacit approval of said behavior.
2) G-d’s commands of others are always given with a specific eye to their walking in sanctification, holiness, and righteousness.
Description ≠ Prescription.
As we read the Scriptures, let’s learn to distinguish and between behavior of others and what the L-rd wants specifically of us.