According to the Bible, when Lot escaped out of Zoar, he went up to the mountains and settled in a cave. While in there, he was seduced by his daughters so that they could bear children and save their family line. Here is the full account of the story incase someone wants to read it.
Lot and His Daughters
30.Now Lot went up out of Zoar and lived in the hills with his two daughters, for he was afraid to live in Zoar. So he lived in a cave with his two daughters. 31. And the firstborn said to the younger, “Our father is old, and there is not a man on earth to come in to us after the manner of all the earth. 32. Come, let us make our father drink wine, and we will lie with him, that we may preserve offspring from our father.” 33. So they made their father drink wine that night. And the firstborn went in and lay with her father. He did not know when she lay down or when she arose.
34.The next day, the firstborn said to the younger, “Behold, I lay last night with my father. Let us make him drink wine tonight also. Then you go in and lie with him, that we may preserve offspring from our father.” 35. So they made their father drink wine that night also. And the younger arose and lay with him, and he did not know when she lay down or when she arose. 36. Thus both the daughters of Lot became pregnant by their father. 37. The firstborn bore a son and called his name Moab.  He is the father of the Moabites to this day. 38. The younger also bore a son and called his name Ben-ammi.  He is the father of the Ammonites to this day.
Crossway Bibles (2011-02-09). The Holy Bible, English Standard Version (with Cross-References) (Kindle Locations 1725-1734). Good News Publishers/Crossway Books. Kindle Edition.
Does this mean saving one's family line is/was so important that you could have sex with your own offspring? Was Lot really drunk to a point that he didn't know what he was doing? Was it a mistake on the daughters' side? If yes, why didn't he(Lot) take any action afterward? Please support your answers with authentic references.