Anyone who did an economics 101 class could predict that forcing such diverse economies with populations reluctant to move to richer parts of the union into a single currency would result in net wealth reduction. [1]
Even the bureaucrats in Brussels knew about this. It was still pushed through because they wanted to accelerate the political union via the currency union, ignoring the financial costs. What they did not expect was the US subprime crisis to hit europe that hard and that early.