I do not have advanced video editors like After Effects, but it can well be a 3D ellipse, the plane of the original ellipse is twisted, like the series in the next CAD program drawing:
The bottom end of the ellipse is fixed, the top end rotates around a vertical axis. It's drawn at angles 0, 45, 90, 135 and 180 degrees. It evolves back to planar ellipse if the twist is continued another 180 degrees but by keeping the top end fixed. The 2nd half of the evolution can as well be a copy of the 1st one, but flipped and reversed.
The same view with fill surfaces shows what it did in 3D:
And the same, but in a tilted view:
In 2D a two node Bezier curve can resemble enough an ellipse and it's simple enough to be edited manually.Or actually nothing simpler exists. It can evolve as wanted if one can manipulate the handles:
These are dragged manually but I guess keyframe animation would make it look smooth if the keyframes were prepared carefully.