> And RIM’s BlackBerry was still the most popular smartphone in the world.
If your world was the USA. Symbian/S60 was the dominant smartphone OS.
> What Miner and Google gambled on, and it seems bizarre in retrospect, was that the carriers and the manufacturers would be good at customizing and improving the user experience of the base operating system.
No, the problem was that the available OS's had huge (leave it to the handset vendor) holes (Symbian), or that their competitors had control of the available 'easyish but hard' options (Nokia dominated Symbian). Or that the other options were crap (Windows Mobile), or required S/W engineering experience which was not easily obtained (generic Linux).
The miracle of Android was that though it had some gaps in it's implementation, was good enough, and sponsored by a somewhat benign entity (at the time).
However, the reason for the handset manufacturers trying to differentiate, no matter how incompetently, or not was that the problem that Android solved also holds a curse. That is that the handset manufacturers do not want to repeat the PC experience of comoditizing the hardware market - What has happened before will happen again - unless we try to retard things.
The only way Google can reduce manufacturer freedom is to become truly non-free, on the day that happens, Android will fork.