Simply, she could be a sociopath. There are many cases of seemingly loving mothers who killed their kids and then seemed unemotional about it. Baby Grace's "mom" is one. Darlie Routier is another. Susan Smith cried but most felt her tears were very fake (especially in retrospect). Bottom line, I think the thought of a mother killing her kid is just so incomprehensible to most that it is in our human nature to find any other excuse than the truth because the truth means to accept that a tiny, little, trusting girl, was destroyed by the person who bore her, who bathed her, fed her, sang to her, kissed her, hugged and held her. Because it is so da*n painful to imagine, and too horrible to believe that the last thing such an innocent child knew was that her own mother, the person who she relied on to protect her and love her, was quietly snuffing out her beautiful, little life. Who the he!! can accept that? So we can't, so we try to create conspiracy theories or kidnapping ring stories, or tales about weird grandparents or evil boyfriends or scary foreigners, or drug-addicted, crime syndicate mothers who somehow sold or stole this child away from her home. Even though there is no credible evidence for any of it. Fact is, there is much more evidence pointing to casey as the intentional murderer of her baby than for any of the other theories pointing to a live child, but some are willing to accept the theories based on little more than rumor rather than the obvious truth based on fact. I do understand why, but I don't think it can change reality.
One last thing: We have been conditioned by crime shows like CSI to believe that there can be no solution to a case if any loose ends are left. However, most cases have a huge amount of loose ends. And no one ever knows with precision what happened or maybe why. They just know that it did. Unforutnately, this attitude has been a great boon to defense attorneys and has been giving prosecutors a huge uphill battle in what previously would have been common sense cases leading to common sense convictions. This case has more circumstantial and actual evidence than many. I think LE is just biding their time and wrapping up their case, but there will be a murder charge. I just hope common sense will once again prevail so there can be a conviction and baby Caylee can finally have justice.