I don't see any big turnarround. It's just Nintendo is smartly selling a mobile device with TV connection as a home console with portability. As a mobile device they won Japan and its good as a present for kids in USA. That's why is selling so well. I woudn't compare it with PS4. It's another market. Graphics wise, power wise, you also can tell that it's a mobile device with TV connection.
The Switch is competing directly with the PS4. That's a fact. I don't know what you even mean with "another market" as they are in the same market. Video game entertainment.