Quote from: BenCodie on Today at 11:24:17 AM

Even after it was taken down, the contracts could be re-deployed and re-used. Truly decentralized. It didn't all fall a part following the takedown and legal issues. Mixers on bitcointalk have never been like this. They are almost always operated by anonymous players, and almost always have custody of their reserves, making them a huge risk to both users and in general.

According to the article, this is apparently the reason:

Quote

“We hold that Tornado Cash’s immutable smart contracts (the lines of privacy-enabling software code) are not the “property” of a foreign national or entity, meaning (1) they cannot be blocked under IEEPA, and (2) OFAC overstepped its congressionally defined authority.”
The six plaintiffs also argued that blockchain transactions can be traceable, which is why some crypto users “want additional options to keep their transactions private.”

So smart contracts are not "owned" by a foreign citizen or entity. This ruling may be a future argument if Monero or any other decentralized privacy service is banned, but I don't think that will apply to mixers.
In any case, the money laundering charges were not dropped