Symbian Won
I used work for Symbian. The OS itself was great at the time (it's open  sourced somewhere), and got security correct (I don't recall 'privacy' ever being an explicit goal) but it was an absolute bitch to develop for. It had its own dialect of C++ which looks nothing like modern C++, the learning curve was huge. It tried really hard to have an app ecosystem but it was nothing like what google and apple have today. Network operators desperately wanted an alternative ecosystem to avoid being dependent on Android and Apple (but mainly I believe so that they could build their own walled gardens).But by the time Nokia took over Symbian it became apparent that they saw Linux as the future OS for high-end devices and Symbian was to be relegated to mid-level devices.