To respond to your bolded while I don't believe in blaming small children I do think there are situations that arise where parents can't possibly continue to keep all children in the home safe if all children are to remain in the home. I'm not saying that was the situation in the Harris family (and given the ages of the children I find it less likely but I have personally seen scenarios where older children were abused by younger children so it is not impossible). As far as going through DHS, I completely agree that is what they should do and from what has come out in the media about this story I think that was what they initially tried to do but it sounds like DHS was not willing to take these children back and threatened them with abandonment charges if they pursued the issue. This could have led to them having their other children removed from the home. I can understand how they have felt like they were in between a rock and hard place.
To answer your questions, based on another poster's timeline, it appears that the girls were in the home for approximately six months before finalization and then another six or seven months after finalization before the rehoming. Altogether they seem to have been in the home from September 2012 through October 2013.
To just share a perspective. We have friends who adopted a child through foster care. She and her husband (who are both pediatricians) really devoted their life to this child. They read books on adoption, attachment, etc before even beginning the journey. Once the child was in the home they pursued various therapies and they kept this child's world small (the joys of practicing together they viewed that although they might not always see each other at least one could be available to their own child and one to the children of their practice with medical emergencies). This child who came into their home at age three was with one of them (no daycare) until she started kindergarten. They struggled with this child from the beginning and really struggled after the adoption was finalized when she was four (maybe it was the age, maybe the honeymoon was over both theories have some support). Over the years there were multiple visits to pediatric sub specialists, child psychiatrists, attempts at medication, etc but things continued to deteriorate. By the time she was six the wife tearfully admitted that they had decided not to have more because they were afraid of what their daughter might do to a younger sibling. She was their daughter and they loved her even if she wasn't in a place to love them and they felt that they had made a commitment to her. They had already rehomed all family pets by this time. When this child was nine the wife did conceive and although she couldn't fathom abortion she strongly considered placing her unborn child for adoption because she believed that might really be the best option. Their younger daughter was delivered at 34 weeks after the wife was physically assaulted by her then 10 year old daughter. The police and child protective were involved but once they were satisfied that the perpetrator really was the ten year old they wanted to consider it all a parenting issue. The DA refused to pursue assault charges against a 10 year old (which I truly believe that the mom only filed as a hail mary pass at help for her child or at least some measure of safety for the rest of the family) and in that state juvenile judges would not adjudicate. The parents made a final attempt to arrange for some kind of out of home group placement which was denied. They then made an attempt to disrupt the adoption were threatened with child abandonment charges (which would have likely resulted in removal of their infant and would have encumbered both of their medical licenses). Ultimately, they chose the best of a bad set of options and arranged to send their daughter to a therapeutic boarding school. The program costs them around $75K per year and even with both parents being physicians that is a struggle. Fortunately they had their house paid off before this happened so they have minimal housing costs and if both parents work full time and they live pretty frugally they can make it work. I know it is a struggle and I know that they both wish they had more time for each other and for their younger daughter who just turned three but they believe this is the only way they can ensure both of their kids are in a safe place and they are sacrificing a lot for that. If they didn't both have six figure earning ability, or if their younger daughter hadn't been blessed with decent health even in spite of her early and traumatic entry into the world this best of bad sept of options plan would not be financially possible. I can imagine that they are not the only family in this situation.
and when that didn’t help, they gave up and dumped them off to whomever would take them in - No questions asked, no background checks, nothing. They wanted to put this chapter behind them and pretend like nothing ever happened and move on with “their” lives, without much consideration for how it would affect their adopted girls. Horrible. And this type of re-homing seems to be MUCH more the norm in the US, sadly, rather than the model way your friends did it. There needs to be much better oversight with a lot more compassion and knowledge about disrupting an adopted kids life yet again and again.