The founders of the monetary union were well aware that the Euro is not sustainable without further fiscal and political integration. But they saw the monetary union as a step on the road to a more general union. That seems to hold up: two years ago, a bank union was formed, and today, polls even in France favor a common defense force.
As to why the EU bailed out Greece’s creditors, I believe you are overlooking the simplest answer. They were bailed out to help Greece. When banks default, the financial system collapses, and the country is send back to the stone age. The EU send boats of gold to prevent this.
Now, it’s a bad thing if a member of a union consumes more than it produces. If your nose consumes 50% of your blood flow, the rest of your body will tell your nose to adjust or be cut off.
The Greek crisis is not about financial gain, but about a long term plan to make Greece a functioning member of the European family.
Listen to Wolfgang Schauble here: https://www.youtube.com/watch?v=qn-s4UrnvAY&feature=youtu.be&t=3370