Perhaps because he wasn't her dad? The previous Judge stated the children were coached, and the mother's bizarre behaviour of which she had apparently accused other men as well.Rememember she was 3!!!!
Oh and she called him "Bill" (why not dad?)
The Judge also stated it was a very weak case but the state proceeded anyway.
It was a very strange situation IMO, because her brother was also a child SO and murderer.
Who knows what on earth was going on in that household at that time? We really don't have enough information about it, and all we know is there were two child victims involved.