The original vision is pretty clear, and a compelling reason to not screw around and get sidetracked, even if that has massive commercialisation upside.
Thankfully M$ didn't have control of the board.
Really really. You have two so-frigging-stereotypical samples of management ineptitude in running a strong commercial brand AND leadership (Osbourne:’guys our phones suck’ ; ’change management 101’: burning raft is literally the most commmon and mundane turn of phraze meant to imply you need to act fast. Using this specific phraze is a clear beacon you are out of way out of your depth by paraphrazing 101 material to your company). If the phones had been a strong product, none of this would have mattered. But they weren’t and this was as clear way to signal ”emperor has no clothes” as possible.
The N9 etc demonstrated there was enough talent for a plausible pivot. Was it business wise obvious this would have been the only and right choice?
The dialect of C++ was pure hell, and the wanton diversity of products meant that there was no chance to get consistent UI over a chock-full of models whose selling potential was unknown in advance. Theoretically, there were standards such as Series 60. Practically, those were full of compatibility breaks and just weird idiosyncrasies.
Screen dimensions, available APIs, everything varied as if designed by a team of competing drunk sailors, and you could always plunge a week of work into fine-tuning your app for a platform that flopped. Unlike Apple, there just wasn't any software consistency. Some of the products were great, some were terrible, and all were subtly incompatible with one another.