Gutzon Borglum was the sculptor and was involved with the KKK. He was chosen because he was the sculptor of the "Shrine to the Confederacy” which was the inspiration for Mount Rushmore.
Guess it shouldn’t be too surprising given the way the land was taken from the local tribes despite it being sacred.
Credit to this comment by u/alcoholicorn that drove me to look it up.
There are pictures of it before the carving.
Though I agree it’s a shame to deface nature the way it was, the label of “sacred” is usually attributed to perfectly mundane things in order to make them special.
The Americas are home to some ridiculously beautiful landscapes. I’d be equally appalled if someone had carved the faces into a part of the Grand Canyon.