The Greek Government and its advisors chose to submit bogus figures prior to attempting to enter the Euro. They used Goldman Sachs to massage those figures and create the business case for Euro entry.
However, the matter does not end there because the other EU Governments did not perform relevant “due diligence” and thus permitted this to occur. They knew, or should have known, what was going on but instead of putting a stop to it they encouraged what was happening, reasoning that EU taxpayers would foot the bill if things went wrong, such is the contempt these taxpayers are held in by those in power.
Goldman Sachs meanwhile argues that they were operating within the rules prevalent at the time.