These results are not too surprising to me. Sure the Switch version is by far the inferior one, but people are not buying Switch for top performance. Instead here are why people like the Switch version:
2. A lot of people want to play this game on the go. Switch is the only way to do that.
3. Collectors prefer carts to discs, because they are more durable and easier to store.
4. People are currently more in the habit of playing their Switch regularly. PS4 and XB1 are old and gamers want to move on to a new console after a while. If the last game they were playing was on Switch (like Smash Bros), then the next game will probably be on Switch too, all things being equal. It's about habit.
Write this in fewer lines and you might have yourself a career in advertising.