The ground floor was most desirable. Less distance to walk upstairs. Upper floors were considered for poor people, because they had to climb more.
The upper floors are most desirable. "View" becomes an important factor when selling real estate. Since the distance to climb is no longer a factor, what you can see out of the windows of your apartment replaces that. The rich no longer want to look at a brick wall, they want a view of the city, and they are willing to pay for it, (since they don't have to climb a damned mountain to see that panoramic view)