What does Genesis 19:33 mean?

Lot's two grown virgin daughters have experienced intense loss. They have witnessed the annihilation of their culture in Sodom, the loss of their prospective husbands, the destruction of their family's wealth and power, and the death of their mother. Their despair was stated in prior verses: they were convinced no men would ever marry them. They would never have children. All they had was gone. They were living in the hills in a cave with no prospects for any kind of better life.

This lack of trust in God reflects poorly on Lot's spiritual leadership. Then again, Lot chose to not only raise his children in a city as corrupt as Sodom, he arranged for his daughters to marry men of that city. That these women would turn to despair in a crisis is not surprising. Unfortunately, this upbringing also seems to factor into their attempt at resolving their situation. In Sodom, the men of the city demanded Lot turn over his guests so they could be raped (Genesis 19:5). Lot's daughters enact a plan, here, which also revolves around sexual abuse.

Lot's daughters concoct a plot to inebriate their father so they can sexually use him, in order to conceive children. Here, Lot's firstborn daughter successfully executes the plan. They see to it that Lot is so blindingly drunk that he has no idea what is happening. His oldest daughter then takes advantage of her father, sexually, in order to conceive a child.