Why does a movable pulley have a mechanical advantage of 2?

A movable pulley has a mechanical advantage of 2 because it allows the effort force to be applied in a way that supports both the load and the weight of the pulley itself. When lifting a load with a movable pulley, the rope is effectively divided into two segments that bear the load's weight, which means you only need to exert half the force required to lift the load directly. This configuration reduces the input force needed to lift heavy objects, thereby providing a mechanical advantage of 2.