Why does a mother raccoon make more than one nest?

It is very common. Odors from excrement or the baby's fur itself will attract predators. Just because a predator finds a nesting site doesn't mean that they will attack immediately. So animals have several nesting sites for safety from predators. Even predators in the wild will have several sites since, should the mother be out hunting, if the babies are found they would be easy prey for whatever adult animal that happened upon them.