Different industries. There are millions of mom-and-pop shops. Tens of thousands of clothing brands. Maybe 20 car manufacturers. A few giant grocery stores. Three bleeding-edge node manufacturers (TSMC, Samsung, Intel). Two mobile OS providers. One bleeding-edge node machine maker (ASML).
The market usually always settles into two popular operating systems because app makers don't want to support more and consumers go where the apps are.
The consumers and app makers choose the winning mobile operating systems. They've chosen Apple and Google. WebOS, FireFoxOS, Windows Mobile, Nokia, Motorola, etc. all failed.