Because he could apparently. He loves Gold Wings but wanted something different. Built it all himself. The Gold Wing owners club people aren't happy. Neither are the GS people. Result! If you're a bit unsociable I suppose.
Who cares what others think.
Its his money and his bikes, its not like they are rare.
Good on him blokes like this make the world a lot more interesting.
Apparently BMW copied Honda's design for the current water cooled engine from this very Gold Wing motor, twin spark, exhaust on the bottom throttle bodies on top