In order to get the loans for this he wound up putting up a ton of Tesla stock. He won’t be poor, but he could possibly lose control of Tesla and likely by extension things like space x.
He’ll likely never be poor but he’ll lose his relevance
But you're right, if he had to sell so much TSLA to meet margin requirements that he lost control, that would be bad.
For the bank, yes. For the investor, not necessarily.
https://www.investopedia.com/articles/investing/121515/how-s...
But to be clear, the broker is very exposed in this situation. It reads like the customer is planning to cover the loss, but if a loss is big enough there's a strong incentive to declare bankruptcy and leave the broker with bad debt. Needless to say the broker doesn't want to be in the position of worrying about whether they will be on the hook for customers' losses. Which is why margin requirements exist.