Tesla are on a mission to solve massive problems for humankind while taking into account modern humans' lack of commitment to solving those problems in a way that would feel like a step back, or that would create discomfort. Tesla's existence as a market solution to the oil and pollution problems is evidence that you don't always need political coercion to solve problems like externalities: Tesla's cars are not only electric cars - i.e. the answer to a problem that could potentially destroy civilisation as we know it - they are also great cars, by any "petrolhead" standard.
As a company and an investment, Tesla's long term mission, its strategy and its step-by-step tactics have been presented in a way that is extremely rare for a company. Most of the work I do for brands this size involves working with a 5-year plan that is nowhere near as clear as Tesla's, and the plans are 5-years because that's when the owners' exit plan kicks in. Tesla's strategy set a clear path for 15 years at least.
So what's not's not to like? I think many investors feel they may have missed the boat on the next great world company. It's quite normal to sit on the edge for a while, to miss out on the opportunity, and to then find a dozen reasons to tell oneself it was good to pass on it.