Varoufakis was the mastermind of the approach to extort the Germans as they would back off and approve a debt relief. It was his masterplan and that's why the Syriza party proposed to him to take the leading role in the negotiations from the position of the financing minister. This has repeatedly been confirmed by all parties, both Varoufakis and members of the government. There's a book coming in September from Varoufakis, called "Adults in the Room" and as certain parts have leaked to the press it has sparked a lot of conversation the last weeks where more and more details of what really happened back then come to surface. Varoufakis openly accuses Tsipras that he backed off of the agreed plan.

The result of such an approach was exiting the EU. To say that Varoufakis didn't called the shots on that is naive. Pretty much everyone understood that if we were to push Germans too much we might end out of the Euro. When Tsipras eventually realized that Junker and the EU had made contingency plans for such an occasion he came to his senses realizing that the bluff has been called. All these are documented in various sources.

The crisis most certainly existed before Varoufakis came into position and no one is blaming him for that. What we blame him for is that he never had a plan and dragged the negotiations for far too long which eventually ended-up with capital controls because we run out of money.