Looks to me that the reason is that the framer didn't put the molding on the wall so that one side lines up with the other.
But you could probably just clone enough of the wall on the left so as to redo the molding on the right, as much of it is visible, to make it higher on the wall. You'll have to work a bit - possibly with both the Clone Tool and Healing Brush Tool, to match the brightnesses. It can also be helpful to select all and deselect the foreground object below before beginning cloning, etc.
I basically used the same method Noel used to achieve this
First I copied and pasted the portion of the wall on the left.
Then I erased some pasted portion to show the front decorations.
I rotated them so they all align roughly with the rest of the wall
Finally I used a combination of Content aware fill and Liquify filter to do the final adjustments.