The only problem is that they were accomplices to something other than what Madoff was doing with their money (in other words, they thought he was perpetrating a different kind of scam in which they themselves were supposed to be the beneficiaries).
It only became a "crisis" when the co-conspirators/victims found out that the scam wasn't what they thought it was.
That was all known. For him to make this last 13+ years without buying any securities is unbelievable.