At the risk of stating the obvious, it seems to me that Madoff (What a name! Almost like coining it for the occasion.), knowing that he couldn't possibly avoid prison decided to see to it that only one of the group would go. His wife, his brother, his two sons, any co-conspirators - all of them will be free to enjoy the fruits of his and their labors. Small price to pay for lifelong affluence. If his plan works.