Let me show why I believe its really smart. Many of us believe the switch will launch with zelda, as it is one the first games to be announced for the switch, and shown off as playable, however, having splatoon will increase the sales for switch, heres why.
People will say that zelda is more popular than splatoon, therefore that should be a pack in, however splatoon has something that zelda doesn't, multiplayer.
With splatoon, I can take my switch to a person's house, and show it off to him/her, but more importantly, I can tell them this – "Yo get a switch, cause this has 2 player, and I can destroy you".
Having splatoon will create competition between friends that will force all of them to buy their own switches so they can compete.
Discussion started at here by famegamedeveloper