It's the Sept. 11 attacks that caused the current economic crisis, not the "Greed on Wall Street".
On Jan. 1st 2001, the Federal Funds rate was at 6.50%. The Feds had raised it gradually from 4.75% on June 30th 1999 to help burst the "irrational exuberance" during the Dotcom bubble.
Having achieved this, the Feds proceed to begin stimulate the economy by cutting the rates 7 consecutive times. On Sept. 11th 2001, the Federal Funds rate was at near historical lows, at 3.50%.
The Sept. 11th attack was intended to hurt the American economy as well as to kill American people. The Feds had to fight the terrorist's intend to destroy the American economy by aggressively cutting an already low interest rate.
Thus, the rate was lowered 6 more times after the attacks to an incredible 1% on June 25th 2003. 1% means that money is basically free. Banks are for profit institutions and they have to compete with each other to lend money out. Otherwise, they would be stuck with "inventory".
After keeping the interest rate at 1% for more than a year, which started both the housing "boom" and the "sub-prime mortgage", the Feds increased the interest rates 17 consecutive times. That started the "housing bubble" and the economic crisis that we have today.
The fact is without the attacks on Sept. 11th, 2001, the Feds would never have lowered the interest rates to an unprecedented 1%. The lowest rate that I can find previously was the 3% on Sept. 4th 1992, in the midst of the last recession.