Yep, I agree, seems like battery failure. They do a controlled descent for most of the altitude, and then drop out of the sky and bounce off the ground/cars/trees (better seen in other videos).

I’ve never done this large a coordinated display before, but have ten years UAV flying experience (quads, hexes, octo, and double stacked octo) and have done smaller scale test flights with a dozen choreographed drones.