Yes, Steve Jobs would have done this, it was part of his vision. And the iPad Mini wasn't anywhere in his vision. But the company has moved on from his vision and they are too scared to rock the boat. Tim Cook is worrying about sinking stock prices, porting to ARM64 would be his death nail.
Intel will make the A processor for Apple, at first. Then they can start collaboration long term about which processors make the most sense. Heck, it may even be a propitiatory processor. Intel/Apple has some interesting joint projects like Thunderbolt. Apple and Intel have thus far played fairly nicely together, better than they have with Samsung.