How does using more pulleys decrease effort?

Using more pulleys in a pulley system distributes the weight of the load over multiple segments of rope, effectively reducing the amount of force needed to lift it. Each additional pulley changes the direction of the force and allows you to lift heavier loads with less effort by increasing the mechanical advantage. This means that while you might have to pull more rope to lift the load the same distance, the effort required to lift that weight is significantly decreased.