You should read about how banks work. Most of their "assets" don't actually exist, they're counting borrowed money as still being theirs.

🌈Fractional reserve banking

Simply put, when enough people deposit money into their accounts, banks will simply take the money and lend it to someone else. It is not "their" money, but crunch enough numbers and do enough predictions and you might make it out.

That's why "run on the bank" is such a feared things - if everyone starts withdrawing cash or sending it to a different bank, the bank can't really do that because they don't have the money.

Yes, it's the largest way money is created in modern democracies