Right, so the new theory is that Madeleine fell, bumped her head and died. Her parents, both medically trained, covered it up by Gerry carrying her towards the beach, maybe to the church, asking a priest to help hide a child's body, but also maybe taking her back to the apartment and hiding her body in a wardrobe.
The police must have forgotten to check the wardrobes, but she must have been in there long enough to leave a cadavar odour for the dogs. Then three weeks later, they managed to get the body into a hire car, without the journalists or police noticing, and spirit her away to some hiding place, which has never been discovered.
They also managed to persuade their group of friends to all help cover it up. After all, Gerry must have been gone quite some time, carrying his daughter's body around the town, asking for help.
Their next step was to get as much publicity as possible, for two years now, in order to keep the story in the news, even though they would surely want it to die down, if they were guilty of anything.