Some peopl;e are under the misunderstanding that because the parents are not showing any emotion publicly then they must have something to do with her disappearance, I personaly thing that anyone who believes this to be true, have no idea about the criminal mind therefore, as I've said before, and I'll keep on saying:
The Portugese Police would have briefed the parents that whoever kidnapped Maddie would get sick pleasure out of watching their anguish, so when attending any press conference to keep their composure and not give whoever did it the satisfaction of seeing them "break down". Does that make sense?