Why does a balloon filled with hydrogen increase in volume as it rises above the Earth?

With increasing altitude, the atmospheric pressure decreases and acts less on the ball.
Any molecules, as we know, tend to move away to the required distance, external forces compensate for this action and do not allow Us, or any other object in the universe, to disintegrate.
Since the forces decrease with increasing height (there is an inversely proportional relationship), the ball begins to increase in size.
If we, for example, put it under water and continued to lower it; then the pressure of the water column, with each distance traveled, would begin to gradually decrease our ball (a Directly proportional relationship would act).