It's all about the scents. He's not physically stuck, but the desire to leave his scent was holding him against the tree.
Rocky Mountain National Park has areas of straight-trunked pines that call me to photograph them. Add an animal, and I'm all in for that image.
The lines in nature running in primarily horizontal and vertical directions result in a uniqueness to this image. Of course, it is hard to make a bad image when a 6x6 bull elk is in the frame.
In this case, the focal length range provided by the Canon RF 100-500mm F4.5-7.1 L IS USM Lens permitted getting the ideal subject framing while moving in front of obstructions — other pine tree trunks. A high percentage of my favorite images are currently being captured with this lens.