Financial Crisis Explained

These two videos are a good introduction to understanding the financial crisis and how it affects institutions and nations but only an introduction there is a lot that I don’t understand. If Greece owes money to the banks and can’t pay then the banks have a problem but since our pension funds are invested in the banks as well as investments from countries like China which have a surplus then we have a problem if the banks collapse. But why should we give money to Greece to pay back the debt to the banks or to pay the interest on the debt. We have to borrow money from the banks to pay off the debts of Greece but we are never going to get the money back from Greece so we’re borrowing to lend money we can never get back. If the banks are in trouble and we have to stop them going under why not lend them the money so that they owe us? My brain hurts.