They do benefit from lending Greece money, those loans aren't free. Though I have to wonder at the logic of lending money when there is so little chance of it being repaid.Greece isn't like Ireland where the government took on the debts of the banks. The Greek debt was run up over 20 years and used to pay the salaries of civil servants, build infrastructure, provide education and social services, and all the other normal functions of government. The fact that it wasn't spend wisely is not the creditors' faults. Given that, there is not a credible moral argument for default.
The only role international finance played was that they helped Greece hide the extent of its deficits, they did not directly benefit from the spending that caused them.