Happy to let Greece off half its debt?

I do not pretend to understand economics. Perhaps someone who thinks they do can explain this to me. 'The biggest gainers were banks, led by French institutions, which are the most exposed to Greek debt.' So says the BBC after the banks write off half the money Greece owes them. Click on title for the article which seems to say Greece lied to the EU about its economy. The whole attitude seems to be keep the EU together no matter what the cost. Looks like another Tower of Babel to me. 'Forgive us our debts' indeed.