Looks to me like 1. The bike is initially rolling straight with no handlebar angle, and then starts falling over to the left. 2. Due to the mechanic explained in the video, this causes the handlebar to turn left.
If there was a human on that bike wanting to turn, here they would continue leaning, turning, and pedaling in the correct amounts.
But because there's no human to keep their weight leaned to the left, then 3. The left turn of the handlebars causes the road contact points to move to the left of the center of gravity, so that 4. It starts turning right.
If there was a human on that bike wanting to turn, here they would continue leaning, turning, and pedaling in the correct amounts.
But because there's no human to keep their weight leaned to the left, then 3. The left turn of the handlebars causes the road contact points to move to the left of the center of gravity, so that 4. It starts turning right.