His wife undoubtedly did some serious hiding of assets already, but there may very well be other assets hidden away which only Sydney can reach. For example, maybe he's got a safe deposit box somewhere jammed full of Rolex's. Maybe he's got another corporation which doesn't have her name on it.
If she really has moved all the assets, then an offer to reduce the sentence he's likely to get in exchange for the return of as much money as possible will be far more effective if he's securely in prison than if he's paddling a kayak from Dubai towards Goa. This may be the test of what his wife loves most: Him or a pile of stolen money.