Not saying that I'm correct, but as I understand the Tesla vision, it isn't "accelerate the advent of sustainable transport that is almost as good as what we make"; it's just "accelerate the advent of sustainable transport". I believe that if Elon woke up one morning and discovered that Tesla had no compelling competitive differentiation to offer the market, he would sell his stake and move on to something new, and be ecstatic about that outcome - Elon would LOVE to see other car companies making better electric cars than Tesla, and at higher volumes and cheaper prices. I believe he would LOVE LOVE LOVE to see Tesla "lose" to better competition, and driven out of business by better competition. (I also believe that he despairs of the other car companies even providing something in shouting distance of competitive - if he's like me, I'm thinking Tesla will be disrupting the entire auto mfg industry, and the only question is who else is going to jump in and help - I see Toyota, GM, BMW, VW Group, Chrysler, and on and on as the Walking Dead - but that's my opinion
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From an investing point of view, you'll want to share that vision, or at least be ready and willing to exit the carousel well in advance of Tesla achieving ordinary competitiveness, as I believe that would mark the end of Elon's direct day-to-day involvement. For many investors, his involvement is an important part of the investment thesis (it may or may not be part of yours).