Who voted it optical illusion of the year? The Optical Illusion Club of Earth?
The image is not rotating on any axis. It's a GIF file composed of forty-six layers. It is forty-six pictures displayed sequentially. And they're not even transparent layers. The layers are stacked vertically then for our convenience the layers are arrayed horizontally in another window as "timeline." So it is a line of images in a row that run in sequence. The last frame leads to the first frame so when the run finishes it continues with the first. It's a loop of images.
The comments at IOTW are amusing. They manage to connect it with the Democrat sham impeachment of Trump.