After the destruction of Sodom and Gomorrah, Lots’ daughters got him drunk, had relations, and bore children. I’ve read many commentaries where people think they did this because they believed they were the last people on earth. I say pish-tosh! They went from being virgins to getting their dad drunk to do their deceptive and perverted deed. That’s quite an extreme! Innocence to perversion.
After stepping back and seeing the whole picture, this is what I came up with….
At that time, Isaac was not yet born. Abraham was starting to wonder if God’s promise was going to come from His nephew, Lot’s descendants. I think the evil one persuaded the daughters to fornicate with their dad so that they could have descendants and appear to receive Yahweh’s blessing and promise of many descendants. If Abraham saw descendants increasing from Lot’s line, then it could be construed as a fulfillment of God’s promise since Abraham is his uncle. But it would be a counterfeit. A false Fulfillment.
I say this due to the similar theme of Abraham thinking that Yahweh’s promise of fathering of many nations might be fulfilled in Hagar. It would technically be in his line but that’s not what Yahweh had in mind.
I’m much more inclined to believe this because we know this isn’t the evil’s one’s only attempt at destroying the line that would later bear Messiah. But I do welcome other suggestions because I may not be correct.