They're drum sequencers, it's a really old way of making scrolling light shows for things like signs and stage displays. They used to use (usually less fire hazard-y) versions of this q long time ago in Vegas for the giant hotel signs and things.

I remember seeing a video of a light display in Cuba. They couldn't get much in the way of controllers so they used a rotating drum of electrical contacts to open and close circuits for animation effects. This looks very similar to that. Pretty ingenious but totally unsafe.

a terribly cropped tiktok video with no link to the source

Arcs don't need to be high current. But this will absolutely fail at some point, how soon is a question.