Even the IMF have admitted that the debt is unstainable. The Eurozone refused debt restructuring, which was the main thing Varoufakis was holding out for.
Without debt restructuring the same thing will happen 5/10 years down the line. An economist will try to fix, politicians like to push it down the line, so they don't have to deal with it.
Some debt needs to forgiven, while economy needs to competitive. Euro deal was the opposite of this.
The IMF has been out to lunch when it was needed most with more reasonable and 'Greek adapted' solutions. Essentially they have forced Greece down a very narrow path that would have worked in Germany but not (in a lifetime) in Greece.
So now we have the end result of that strategy (which both the IMF and the previous Greek governments as well as their lenders are party to).
Varoufakis is a very smart man that made a whole bunch of moves that make no sense to me, I think that the last 6 months have pushed Greece into a corner taking away whatever manouvring room they had and now there are only (very) tough choices left.
Going after the tax dodgers with a really big stick should have been the first order of battle for instance, now it is very late to start to solve this in a structural way, it's chaotic at best and catastrophic at worst.
How the EU will handle this will be a defining moment in their history and will potentially make or break the union in the longer term.
Without debt restructuring the same thing will happen 5/10 years down the line. An economist will try to fix, politicians like to push it down the line, so they don't have to deal with it.
Some debt needs to forgiven, while economy needs to competitive. Euro deal was the opposite of this.
That's what has caused the rift.