There's almost certainly a scientific explanation for this, as I'm sure will be discovered later, but in terms of metaphysical symbolism, it might be a manifestation of sympathetic magick - the universe trying to hint at events going on behind the veil. Circular group movements are frequently used in rituals to cast spells, as they embody the circulation of life energy, like a particle accelerator, or Stone Henge. The sheep(le) mindlessly dance to empower the idea represented in a particular manifestation of 13's occult numerology. The 13th tribe/bloodline, perhaps? A Christ or antichrist figure (12 disciples + 1)?