Most importantly, if the McCanns had done their job properly as parents, there would be no need for any of this.
There's a good point, well made. Who started all this? Did the police kick the McCanns out of their apartment and insist they left it unlocked to assist anyone that may want to abduct a child? Did they insist they did this night after night? Did they force the McCanns, under duress, to leave their children in a dangerous situation? (as evidenced by one of them going missing, can't get much more dangerous than that, eh?)
Some people, naming no obvious names, made a judgement call to do all those things voluntarily. Had they exercised what most people would agree is even a modicum of common sense then they wouldn't have been in this position, would they...? Regardless of how Madeleine came to be missing, one way or another it was all, 100%, caused by the initial decisions made by the McCanns.