On more serious note, after Wii U faile, I think its very obvous why Switch is selling great:
-Appling and very intresting hardware in form of hybrid, some people still dont understand that Switch is aiming handheld and home console market in same time. Also it has very good value like real home console and real handheld in one, and two Joy Cons for local multiplayer out of box.
-Huge system seller games from start. Zelda BotW is huge system seller game, that is followed by MK8, Splatoon 2 and soon we will have another big one Mario Odyssey even Switch still didnt meat demand and there are still stock problems. Also, steady flow of games, Nintendo is releasing basic one stronger or bigger game every month.
-Good marketing and branding, its totaly on spot people heard for Switch and they know what Switch is about.
Intresting, those are all things that Wii also had and on which Wii U totaly failed.







