. . . it's the gremlins in the center of the earth dontyaknow.

(from the YT post itself)

The rules of plate tectonics are largely intuitive. They state that the Earth’s tectonic plates do not move randomly, but rather evolve in a manner that is consistent with the forces that drive them. The principal forces are slab pull, ridge push, and trench roll-back. Understanding how these forces work provides important insights into how plate boundaries will evolve through time. Simply said, plates move only if they are pulled back into the mantle by a subducting slab or pushed laterally by a mature mid-ocean ridge system. In this animation, the evolving plate boundaries have been drawn to follow this maxim.

@FearlessFly well, that's interesting, but I think I prefer "gremlins"......