There's a reason that it's called economic policy.
Bad policies lead to bad decisions which often lead to calamity. Any systems analyst will tell you that.
As it's the Fed's job to direct monetary policy in the first place, the logical place to look is there first. While the big banks like Lehman certainly have a role to play, placing blame squarely on them laughs in the face of looking at your overall system first, before scapegoating banks and other financial institutions.