Yeah perhaps it could be a rocket, but it moves in such a slow, controlled manner.

It could be very far away and very high. So you see it slow, just like a plane movement far away.

And some of the people filming are close enough that you'd expect to see something more at the front of it in that case.

Rocket itself is very tiny, relative to the gaseous tail spreading wide on the edge of atmosphere, where it expand widely without nearly any resistance from the air.

When it ends there's no explosion either, just that ominous-looking black void.

Fuel just burned out silently, so you just see black sky through the expanding hole in gases.

Truly a unique looking phenomenon.

Absolutely. Even without spiral it was an amasing entertainment. I saw something with multiple engines, it looked like giant strings expanding behind rocket for a while and collapsing again into the twined rope-like tail, faiding in night sky, when second stage began to work, tail color and number of strings changed. Then tail is just cutted off, and giant twined two-piece rope in the sky slowly faded out.

Unfortunately there is no flidghtradar24 like service to show rocket launches, so it could be hard to check my theory. :)

Really, I tink that aliens, or who they are, would not make a large scale entertaining light shows in the sky for us. Yet. :) Usually they hide carefully, and all we have is murky blurry spots on shaking camera.