Google screwed up when they bought Motorola.  

None of the Asians trusts them any more with their future success.   They all want their own tame OS that they control.   They also want the big bucks they see out there in software.

Google is gently corralling them now by controlling who gets into the Play Store, but this is being countered by the Russian Yandex app store an alternate App Store that is available to anybody.  Most of the app writers are putting their stuff into as many app stores as they can find in order to try to make a buck.

Steam is also now a software parking place that gives 75% of the money to the app writer which is a good bit more than anybody else does.   If Steam keeps it up they too may become a Play Store competitor.