The financial crisis was caused by a cocktail of shortcomings in different areas, such as regulatory loopholes, monetary and fiscal policy mistakes, macroeconomic imbalances and insufficient risk management practices in systemic financial institutions in an environment of dynamic financial innovations. Thus, I would be very sceptical regarding overly simplistic explanations for the crisis.
But all these deficiencies led to exaggerations in different sectors and countries. When these exaggerations suddenly reversed themselves, the crisis emerged and affected the world economy in a way not observed in post-war years. During the crisis, fiscal and monetary policy both played a decisive role in stabilising the financial markets and the real economy.