What I've heard from people associated with Tesla over the years is that the battery management and packaging technology is their main technical innovation.
It allowed them to use existing battery chemistry and cells to provide incredibly high power output (Ludicrous mode) while also preserving the lifetime and capacity of the battery, which is no simple feat.
Someone who works at Tesla/Solarcity told me recently that the same approach is behind the Solar Roof: existing PV cell technology but with very novel packaging.
This is, in general, Tesla's real advantage: top class systems engineering. EV's will be a commodity item in the near future, but the underlying systems will not be. I expect Tesla to dominate the software side of things, including battery management, autonomous, etc.
From a technological perspective, they're simply applying green solutions via battery innovation into the automotive industry. Simple as that. Anyone else can also do it, such as Chevrolet with the Bolt.
What makes them different is how they have captured the public's imagination via creating incredible supercar-like performance purely using electricity.
What they've essentially done is solidified the public perception of Tesla being at the forefront of a revolution.
It's the same thing that makes something like Apple special. On a cost-performance ratio, if you build your PC from scratch, you will likely get better specs and performance for a much cheaper price. But it won't be an Apple device or enact within the apple ecosystem.
Someone will probably build a better 100% electric car (eventually) but nobody will have the same level of cultural cache. There will always be nitpickers who can say that the eventual BMW/Audi/Ferarri electric car is hotter than the Tesla, but it will never be as revolutionary as Tesla.
Tesla, Apple, Google, Facebook. These, and likely a few more companies, have transcended their mediums to make them truly special not only within their respective industries but societally as well.
It allowed them to use existing battery chemistry and cells to provide incredibly high power output (Ludicrous mode) while also preserving the lifetime and capacity of the battery, which is no simple feat.
Someone who works at Tesla/Solarcity told me recently that the same approach is behind the Solar Roof: existing PV cell technology but with very novel packaging.