Why are there two sun shadows in the photo when shooting the sunset?

Obviously, you should get an answer: look with the naked eye, shoot with the camera, it is there, so it is obvious that the camera itself makes it appear.

The reason for it is actually the name of that thing: lens halo. Because when the light enters the lens system of the camera, it will be reflected on the mirror, resulting in multiple images, which is an illusion.

Unless you can eliminate the reflection of each lens, it will still appear.