lack of autonomy

This is one of those weird legal things that extends from prior to the modern era. In previous centuries people could own slaves regardless of culture or region.
Even Christianity condones slavery.
Leviticus 25:44-46 and Deuteronomy 23:15-16 are fine examples of how the Bible was used to continue slavery and racism into the present day.

Sexual slavery, or being sold to be a wife was common in the ancient world. Throughout the Old Testament, the taking of multiple wives is recorded many times.[42][43] An Israelite father could sell his unmarried daughters into servitude, with the expectation or understanding that the master or his son could eventually marry her (as in Exodus 21:7–11.) It is understood by Jewish and Christian commentators that this referred to the sale of a daughter, who "is not arrived to the age of twelve years and a day, and this through poverty."[44]
Source: Wikipedia

Although not referred to as such, parents "own" their children and in modern culture keep them trapped in the eternal childhood that somehow becomes adulthood at 18.

Children cannot give consent because they aren't allowed to give consent. At the same time they are not trained or allowed to think critically. It's even worse when they get forced into purity culture and have to live under a strict code of behavior that targets girls and women.

So what does that have to do with incest? Thus is merely lack of choice. They were curious, horny, and really couldn't reach out to anyone else.

Just my two cents.