In my heart of hearts I honestly believe Caylee died as a result of narcissistic rage.
I think many here have had first hand experience with a disordered personality. Perhaps my living with someone dx'd comorbid APD/NPD causes me to have empathy towards GA/CA.
To be fair by the point ICA was exhibiting full flared characteristics associated with PD she was an adult and CA/GA could not have forced her into treatment. Cluster B PD's are notoriously difficult to treat and therapy remains largely ineffective anyway.
While I believe this family is steeped in several other MH issues I think it important to remember how insane living with someone who is disordered can be. You, because you love them, are desperate to believe them. You cannot comprehend someone who has no conscience, essentially no soul, because you are not wired the same.
Disordered people have the power to convince you the world is flat. They are skilled manipulators - dangerously deceptive predators who study their prey. They learn your weaknesses and play off of them. They are psychological abusers - a walking, talking, living nightmare. At some point you seriously wonder whether there is something wrong with you - after all, they appear to be this wonderful, loving, amazing person and yet you know there is something not quite right. Should you mention this feeling you will be in for a barrage of gaslighting.
I cannot say GA/CA should have, could have, because it took me more than a decade to be capable of walking away from my disordered ex. What I can say, with great confidence, is that GA/CA will always tell themselves they should have, could have... they will be forced to live with the hell ICA created, thrust upon them, for the rest of their lives. They will forever wonder what they could have done differently and they will always struggle with forgiving themselves.
JMHO