The stock is fascinating to watch because of how binary the perception of the company is. After doing some sophisticated psychoanalysis™, the sharpest distinction I've found between the two opposing viewpoints is design. People who don't understand Tesla tend to be the same people who didn't (and still don't) understand the iPhone. For these people, the Model S is just another car, in the same way that the iPhone would have seemed like "just another cell phone". The idea that "just another car" is going to beat companies that are already making cars (and have been doing so since forever) doesn't make sense.
Related to this is people getting stuck on the idea of an "EV market", which I don't think was ever really a thing. Tesla has been competing in the same car market that every other car company competes in. The electric drivetrain may be a major factor in enabling a superior design, but most people don't care. I think many short sellers are attributing Tesla's sales to "EV buyers" rather than to "people that buy cars that are better than other cars". These are two very different beliefs about what's going on.
The financial arguments are (in my opinion) largely after-the-fact rationalizations.