I ran an example earlier. But again for simpliciity, I am ignoring interest. I have $10. Bob borrows $10 from me. He runs into Chris who needs money and Bob lends him the $10. How much money is there? Still $10. What is changed is that now Chris owe Bob $10 and Bob owes me $10. The total amount of money is not suddenly $30. It is debt of $20 plus $10 in real money. Bob and I have zero dollars and Chris has $10. We are owed money but don't have it. Same for the bank depositors.Get out some monopoly money and try it amongst three people.