Maybe an attorney will chime in here and enlighten us to other reasons but yours sounds logical.
What is odd that the defense lawyer did not question further what appeared to be perjury by Mrs. van Dam.
I've read about several other cases where a child was kidnapped at night from her own room -- but I can't recall how the kidnappers took the children.
Hannity has commented that he believes the right man is on trial. Although the life style of the van Dams placed the children at risk and this might never have happened if they had been more concerned about the safety of the children, this does not mean they murdered Danielle. There is the forensic evidence against Westerfield, especially the towel and the blood on his jacket.
Many on FR have disagreed with me when I've said that parents have to be very careful about the people they allow into their home and to protect their children from sealzy elements. This case helps to support my previous arguments.