Gorgok

All the inputs make sense in that video, nothing is essentially backwards of what its supposed to do. Collective gives it thrust, rudder keeps the nose up, and aileron controls its roll. He is rolling it to the right the whole time, as his inputs show, and combined with the other inputs the heli tries to fly towards the center (actually a little past the center) all the time. But since the heli changes its position and angle the whole time, and the point at which its trying to go changes, it just ends up in that pattern. Change the roll and thrust and the circle gets bigger or smaller.

I think it would be easier to visualize if you thought about it flying nose forward through that same circle (since for all the heli cares the orientation is all the same). You give thrust, roll on its side, then pull hard back on the elevator. So long as you get the thrust and elevator right you make circles on your side. Now rotate the tail 90 degrees clockwise and you are flying nose up with right aileron going left. Another 90 and you are flying tail in pushing the elevator forward. Another 90 and you are nose down with left aileron going right.

In some sense its the same as a car/plane/rocket on a string. The thing wants to go in a straight line (in the heli's case its straight in to the center), but the tether keeps it changing direction (the roll caused by the ailerons). Cut the tether and the straight line starts.