1. For a bank run on an actual bank, it is known that a bank doesn't keep all your assets on hand - they are loaned out, which is (largely) what allows you to earn interest. So it is known that if everyone tries to withdraw at the same time that there won't be enough money.
2. For an exchange/brokerage, your money/assets are explicitly NOT supposed to be lent out without your permission. So, in theory, if everyone asked for their assets all at once, the assets should be there.
1. For a bank run on an actual bank, it is known that a bank doesn't keep all your assets on hand - they are loaned out, which is (largely) what allows you to earn interest. So it is known that if everyone tries to withdraw at the same time that there won't be enough money.
2. For an exchange/brokerage, your money/assets are explicitly NOT supposed to be lent out without your permission. So, in theory, if everyone asked for their assets all at once, the assets should be there.