If you own literally all of the stock in Tesla... how could the stock crash? There's no stock being traded for its value to change.
Of note, there are examples in the past of companies going private without falling apart--Dell is the most notable example I can think of off the top of my head.
If nobody is bidding, there's no asks to cause the price to go down. More likely, someone buying all of the stock either a) intends to take it private, at which point there is no more stock anymore or b) intends to fold it into another company, at which point there is no more stock anymore. (Of course, the valuation would likely go down anyways, because people usually pay a premium to buy all of the stock.)
Of note, there are examples in the past of companies going private without falling apart--Dell is the most notable example I can think of off the top of my head.