None of the replies have hit the nail on the head: the money isn't in the jurisdiction of the sheriff. When a (street) drug dealer is caught, the cash is right there and can be seized. With this type of crime, it is elsewhere.

For the same reason that you never see a SWAT team breaking down a rich criminal's door to arrest him, even if he has body-guards or registered firearms, or is accused of a violent crime.

(Yes, I know, someone will find such a video on youtube to prove me wrong).

To state the obvious, because it's a billion dollars and the defendant isn't from south of the border.

Not condoning it, just suggesting that's the real reason why.

Justice dept probably froze that already pending trial