Cashing in on the credits is part of the present business model, not some fluke that keeps Tesla afloat. Remember, without government intervention there would be no GM or Ford or Chrysler and that doesn't include oil subsidies over many decades.
Yes, there is no rational for Tsla price. But the naysayers wouldn't have bet 2 years ago that Tesla could be in the S&P in 2020 either. Tsla crash? Go for it, short it and tell us all how it feels.