Maybe this “space” thinking is wrong. Don’t worry about the “smart watch space”. Worry about making a product that will make a bucket load of cash. Does it matter if the sector is worth much overall when you rake it a butt load of money for yourself?
By that measure, the iPhone is a total failure, together with the smartphone market it created. It pales to insignificance compared to the market for food! And don't even think of looking at the market for shelter, then it's hardly even a joke, why bother. Or maybe that that's not really a meaningful angle of looking at markets?
What exactly is the "all that money" you talk about anyways? If Apple's watch division was a separate entity on the stock market and they had inexplicably high valuation I might enthusiastically agree with you, but it's not.
Neither butts nor boats are all that large though. Even if Apple has made both boat loads and butt loads of money, we would need to be talking about gigabutts or kiloboats to get anywhere meaningful.