Greece is the geo-political soft underbelly of Europe. It is also a historical lynchpin of the European historical 'story' supposedly going back thousands of years and being the first to incorporate democracy. Germany after all is less than 200 years old and can boast of both a raft of important mathematicians and the Holocaust. Much of German history of more frightening rather than inspiring.
More to the point, if Greece exits the Eurozone sphere it will certainly fall under the orbit of another power, perhaps Turkey or more likely, China. The latter already runs the Greek ports, and could utilize them in a monopolistic way to wipe out much of European manufacturing.
In short, the European leadership is being myopic if they think they can just let Greece go and all will be well. But one would expect no less. This is a continent where educated sophisticates can belittle Slavs as 'primitive' (compared to 'Czechs'), or a Southern Italian can be characterized as 'African' - all over Opera and fine Swiss chocolates - leaving an outsider nonplussed (personal experience). For myself, I prefer 'race mixing' and a lot of it.