Germany is not that strong as many are thinking. "We" are a export-nation. Without a strong export the unemployment will rise hard. It's in german-interest to keep the south in the game because it could be the end of the Euro if south-states would leave. And that's why our government is in a weak position. They won't pay the demand for WW2 but they will make concessions. But, it's just playing time (delay the dynamic). It won't help long. It did not help in the past it won't stop the dynamic.
"strong" is a relative term. Compared to a bunch of bankrupt olive-munching crybabies, you are pretty strong. Ship your cars over here and we'll buy 'em if the price is right. Us Yankees love German cars. Seriously, you extended credit to poor countries so they would buy your stuff. That was not a good business decision, but don't compound it by throwing good money after bad. Varoufakis was correct when he said they were broke and can't pay you back.
The debt needs to be written off and the longer it takes to do so, the greater the damage. But Greece has to leave the EU. The other debtor countries will run all over you if you don't stand firm.