But i find several things suspicious, like:
1- How come Elisabeth never tried to attack him or kill/injure him in order to escape if she supposedly didn't like being trapped? I don't think it was possible she was tied 100% of the time down there, she would have died quickly if that were the case.
She could have punched his throat, eyes, kicked his privates, etc. She could even have tried to seduce him to get him into a more exposed position and then attack.
I think there were objects down there she could have used to attack him as well.
2- With so many people in the house, they never saw him taking food down there and other things? They never heard a single thing? They never noticed anything? He had 7 legitimate children mind you.
There are some other things i doubt, but mainly what i doubt is that this case was all about him being a monster and the daughter being a helpless victim who was desperate to escape.
He was a monster for sure, but it doesn't look like she really tried anything to escape or end the situation.
If it was all totally against her will, where's the fight? Where's the attempt to escape and do something?