85% good enough, is more than enough to win a market if you have substantial other advantages in your favor.
Windows has always suffered fragmentation, and has rarely been better than 85% good enough. Circa 2002 they had '95, 98, ME, and XP spread across over half a billion units. With further varied patch configurations and service packs. The total global varied combinations are in the hundreds in that context.
But, you say, that's just so horrible! Welcome to reality, where markets are never dominated by perfection and fairy tales. You don't have to like it, you can rail against it the rest of your life, and fight the good fight; and Android will continue to dominate, and it will have absolutely nothing to do with issues related to fragmentation.