However, at the core of the crisis was the inadequate understanding and measurement of risks and funding of assets with shorter term liabilities on a large scale. There was aggressive easing of monetary policy in the US after the bursting of dotcom bubble leading to very low interest rates.
The long term yields in the US were also depressed on the back of global imbalances as the huge reserves built by  2  BIS central bankers’ speeches  countries, specifically China, found their way back to the US treasuries.