Tesla is certainly a solid business in the sense that they make cars people are happy to buy. I certainly wouldn't expect the value of the business to drop to zero.

But Tesla has a Price/Earnings ratio of 100 while other car companies like Toyota only have a P/E of 10. So Tesla's stock price could drop a long way while still being reasonable.

And if Musk had got a loan against his Tesla stock to buy Twitter, a substantial drop in Tesla's price could have disproportionate results.