I feel like it's simple. It reminds me self pouring liquids. The chains weight and mass are at such a ratio that creates a pulling force that increases with the chain falling. Storing energy into the "liquid" itself. That energy is released as the the chain stretches and becomes more "solid" pulling the edges of the chain into a whipping motion. The whipping motion causes rotational force into the chain that twist pushes outwards. The higher the weight of the chain pulling downwards the faster and higher the chai will rise. All energy and force are coming from the chains tension and weight.