I think an overlooked aspect is arrogance. I've seen many mentions of it over the years (Peter Chou, leading the way I guess). There's a subtle balance between leading the way and listening to your customers.
HTC will find something hot, then sit on it too long. Or come up with ideas like Ultra "no, low res is totally good enough" Pixel and again, stagnate. (Versus slowly creeping up the resolution, keeping an actually usable tech like OIS versus idiotic dual cams, then throwing in the towel a couple years later.)
Also, and I know the US carriers and others certainly are to blame a bit for this, but 8 million subtly different models...
Just do a basic approach like:
Cheap, midrange, flagship.
After phablets arrived? Each available in normal and humongous sizes. That's it. Maybe the stray tech demo niche like product (something like the 41mp Nokia's).