The family wanted a real master bedroom and 2 children's bedrooms on the second floor. Taking down the walls at the top of the stairway, co-opting a bit of the hallway, setting the door on an angle, and combining the 2 smallest rooms provided sufficient space for a master bedroom that fit the owners' needs — and their furniture.
The extremely cramped children's bathroom was made much more useful by converting the existing linen closet space into an alcove to fit a vanity
If you're wondering where the "Up" stairway is going, there are additional bedrooms on the 3rd floor. It was also an apartment at one point, and is now the family's guest suite.