This information comes from a Wired interview with Zelda producer Eiji Aonuma…
On Miyamoto stepping back a bit…
“I’m actually the one who was the most affected by Miyamoto taking a step back, because now I have to take on all the responsibilities of Zelda. I thought, hey, this is my chance to create something I really want to create!
Miyamoto is God, so even when I say, hey, this is what I think should be done, they’ll always question: ‘Well, what would Miyamoto say?’ Up until about two years ago, Miyamoto actually had a lot of comments and advice about Breath of the Wild.”
On having it be a single-screen experience…
“We realized that having something on the GamePad and looking back and forth between the TV screen and the GamePad actually disrupts the gameplay, and the concentration that the game player may be experiencing. You have your car’s GPS system on your dash. If you had it down in your lap, you’re going to get into an accident!”