The problem is that the charges are against the property itself, and it's a civil not a criminal charge. So the police only have to meet a minimal standard that there is probable cause. This could be as simple as claiming the only reason someone wouldn't be actively seeking that large amount of money through legal means would be that the money was involved with or acquired through illegal means.

If the police did seize the money, it would at least be tied up in court for years with extended legal expenses. Personally I would rather take my chances on laundering the money or an extended period of time.