Momentum. Tesla got an early start. A decade means nothing. Ford was founded 115 years ago.
Here's the problem. Tesla's cars have two key things that make them competitively interesting: Autopilot and their electric drivetrain. Take those away and their cars are a special kind of "offensively uninteresting". The interiors are horrible, deserving of a car half the price. The build quality is inconsistent. The tech is pretty cool. Parts are unavailable.
So, start with autonomous. Which is easier: for another company to achieve autonomous on-par with Tesla, or for Tesla to fix the design and engineering problems they've been having? 3 years ago, people might have said the latter. But today, we can name 3 companies who arguably have on-par or better driverless tech than Tesla (Google, GM, Uber). There are cars you can literally go buy today that get 90% to what the Model S does (2018 Audi A8, 2018 Accord, 2018 Cadillac CT-6). In some cases, they do better. Where's the competitive advantage?
Electric drivetrain. Tesla is still leading here. For how long? BMW will have an electric mini out in 2019, an electric X3 out in 2020, and 25 all-electric models by 2025. Audi will have an all electric Q6 by 2019, you can put a pre-order in today, 310 mile range. Toyota is planning 10 EVs by early 2020s. Ford is releasing an EV performance car in 2020 (huge missed opportunity to resurrect the Thunderbird brand, as they went with "Mach-1"). Volvo just spun off Polestar into a performance EV brand. The list goes on.
Tesla's massive investment in energy development will be the single thing that might save them; if they fail at making cars in 6 years, at least they can sell batteries to the companies who, well, know how to make cars. But, oh guess what, VW is sourcing their batteries from LG Chem and Samsung. Toyota is making them in-house, and they've said publicly they've achieved a "research breakthrough" on solid state batteries they aren't sharing [1].
I want Tesla to succeed. But, frankly, they have about a year to get it together. That means fix their QA issues, up the interior quality, get autopilot working, drop prices across the line. Possible? Honestly, it doesn't seem likely. But I'm holding out hope.
[1] http://www.autonews.com/article/20171026/COPY01/310269958/to...