This effect is much easier on a more stupid camera.
With any old DSLR, set it on a 1 second to 30 second exposure, open the shutter, and swing the camara around a bit in front of some bright Christmas lights.
But the iPhone 13 is a very clever beastie, with a built in assumption that anything looking like this is an accident, AND IT’S GOING TO *FIX* IT FOR YOU!
But when I want to get this effect, then I have to trick the iPhone into doing what *I* want, not what some software designer in Palo Alto assumed (incorrectly) that I would want.
It’s a challenge. Practice, practice, practice!