I mean they still had ~$50 million in cash on hand, plus some teams and prototypes. I certainly wouldn't have invested, but if you have $50 million, the potential to sell more stock, and a prototype there's still a lot you can do.
If a business has $50 million in cash on hand and no significant liabilities, the business is worth at least $50 million, no doubt.
However that still leaves $29.95 billion of the $30 billion valuation unexplained.