Symbian - a post mortem
Nokia chose Symbian in late 1990’s - an eternity ago. They were targeting something like the 9210 Communicator and the 7650 - devices with 8 (4) megabytes of RAM and 4 megabytes of disk (the 9210 did come with an additional 16 megs of disk in the form of an MMC card). At that point in time there weren’t that many options. Linux wasn’t really viable for such specifications. Windows CE was around - but let’s face it, it’s still not a great choice, let alone then. The previous Nokia smartphone (not that the term was widely used yet) was the 9000/9110 Communicator which ran GEOS (of all things), and was probably seen by Nokia as a dead end by then.