Well, I disagree. Nikon's problems have everything to do with the quality of the cameras and lenses they did or did not produce 5, 3 and 1 year ago.
Quality defined as their ability to various needs of photographers. Sorry, no more time today on this.
Cheers,
Bernard
So, let's just say Nikon had the best camera at the best price point in the market 5, 3 and 1 year ago, with everything else remaining the same.
They'd still be in the same situation. They still wouldn't be able to produce a sensor on their own. They'd still be completely reliant on Sony and Sony subsidiaries for their high-resolution/high DR sensors - Sony could still just turn off the tap and they'd be in a world of trouble. The would still be competing for market share in a shrinking market, unable to supply anything to anyone other than non-smartphone photographers - they have no sensors to sell to phone manufacturers, don't make lenses for anyone other than Nikon cameras and other Nikon products and don't produce much of anything apart from stills cameras (whose market is shrinking) and a bit of technical equipment.
Meanwhile, look at Sony, who, ten years ago, didn't even have a real stills cameras business to speak of (point-and-shoots notwithstanding). What they did have was cash reserves, other income streams and control over their supply chains (i.e. they could develop and produce it themselves). Now they've taken over several other companies' camera/imaging divisions and have several others (Nikon, Pentax, Phase One, etc.) essentially beholden to them, as well as a booming business making sensors for the non-photographic technical and smartphone markets.
Dedicated still-photography cameras are a shrinking market. If you can't offer a product that works for other things and ties into your camera business (e.g. Sony's sensors and their use in phones, video and other gear, or Zeiss' optics), you're either going to become a niche player (like Leica) or die. And, in the consumer electronics sector, niche players are really only a small step above dead, since they lack the scale to innovate at the level of the big players.
Nikon is too big and has too much overhead to become a niche player. Their best bet is to expand on their optics capabilities, produce high-end lenses for every other mount out there (as well as for phones, security equipment and everything else which needs a lens) and generally act as a rival to Zeiss. They do a bit of that already, making medical lenses, rifle scopes, binoculars and the like. But their camera business is so vulnerable to competitors' moves at many different points of development and production that to rely on that as their core business is to bet the company on the goodwill of their competitors.