> billions of dollars that they dont even have

Companies don't ever "have" things, they are themselves things that people have. There isn't a fundamental difference between taking a loan smaller than their total capitalization or spend some money they have liquid at the bank. It's both taking money from the shareholders and spending on something.

That said, yes that investment is stupid and deserves quotes around the word. But making risky investments when the company is operating in the red isn't stupid at all... it's just that this one isn't risky, it's certainly bad.

If you can borrow money at X% and make (X+1)% on that money, you do that and invest it. As an individual you can do that by buying stocks on margin.

You can also do it by buying risky stocks and pretending you're buying alpha!

Wait until you discover that the bank doesn't have those dollars in your account.

It mostly does. Treasuries are a kind of dollar.

They could cash out everyone's account from the Scrooge McDuck pile of gold in the vault?

Up to $250k per account yes. The bank would fail but you'd get it over the weekend.

The FDIC currently holds a reserve of 1.28% of deposits. It can handle a single bank run, but not a widespread one.

They don't usually touch the reserve. They tell a bigger bank to buy them over the weekend and back it up.

Afterwards they can use that, charge the other member banks or reopen: https://www.federalreserve.gov/financial-stability/bank-term...