Though internet companies aren't the best at cash flow management either, it is more about getting the market / customers then the profit. I think innovation is excusable for revenue/profits for some time.
Starting an electric car ONLY car company is even harder than having it as part of an existing car company like Mercedes is doing well with.
The shorts are mainly trying to kill Tesla and coming from the oil, gas, other auto companies most of all. Lots of games are played with car companies (see VW short squeeze a historically big one) because they can't react as fast as it is hard work. I think the shorts have been not just focused on profitability but to drive out the competitive threat, the shorts have also been attacking Elon Musk non-stop.