Dennis Howlett covers this issue well.
I find this story amazing. I've run an audit firm. The audit partners were tough on each other and the quality of their work. Rightly so. And every audit was hot reviewed before it went out by a second partner. Of course it took time, and it cost. Achieving high quality does.
Why did Deloittes find it impossible to reach that standard? Lack of willing? Greed? Incompetence? It's hard to find another reason.