These people were lazy and selfish. Pure and Simple. Calista reportedly had mental and physical impairments therefore she was not able to defend herself, she was not able to tell someone how she was being treated and her 'parents' knew this and took advantage of it. They could put Calista to bed with no sheets or blankets with a clear conscience because Calista probably never asked for bedding so they could tell themselves - she doesn't want that. They could chain her to the bed with a clear conscience because Calista didn't complain and they could tell themselves they were doing it for her own safety. They took advantage of her disabilities to make things easier on themselves.
There is no doubt in my mind that the 'mother' did not try to save Calista. She ran out of the house and saved her own life rather than risk it trying to unbind the bounds she herself tied earlier. She knew Calista was in there alive, chained, struggling to get out, she knew that Calista was going to be burned alive and she made a choice to let that happen. I bet the other two daughters got out safe and sound, didn't they?
As far as comments made about these people being animals, humans ARE animals but I get the sentiment and that is insulting to animals. Animals (with few exceptions for certain situations) take care of their young, are attentive to their needs, feed them, bathe them, protect them with their own life, a mother cat will re-enter a burning building over and over in an attempt to save her kittens, they teach their young what they need to know before they reach maturity, they are never intentionally mean or cruel. Humans are the only animal that is cruel for the sake of cruelty. These people were acting Human, explicitly human. I am glad they were charged with homicide and I hope they are convicted. I would also like to see DHS employees who were idle and complacent with the knowledge of how this child was being treated and chose not to do anything face consequences.