Appears to me that, when they had the toilet sitting in the now-carpeted room as contractors worked on the flooring in the bathroom, a contractor tasked with applying carpet to the room the toilet was temporarily being stored in had a typical "not my job" moment and laid down the carpet everywhere except where the toilet was temporarily being placed.

You can even see the garish cut the contractor made on the right hand side of the hole so he could get the carpet to lay into the corner, behind the toilet, instead of simply moving it.