Apple focuses pretty strongly on innovating by thinking about how people use their products, and also what consumers want from the products. There can sometimes be a gap between those two, and that's where they concentrate.
It's all just an indication of the old saying that nothing succeeds like success. If a market is booming, and people are looking for products, there will naturally be companies happy to provide them.
If what Apple provides as a hardware platform is interesting to the open-source community, it would not surprise me very much that a group of people will find a way to port Linux to that hardware in short order.