I feel like your downvotes are undeserved. From an engineering perspective, all Tornado did was add anonymity/plausible deniability to the blockchain--which is all that ZK will do. Maybe there's a question as to whether OFEC will also see ZK as money laundering, but my guess is they won't until it gets to a certain scale and then they will--exactly like Tornado. That limit was ~$7 billion, which is < 1 FTX, and far smaller than the current market cap of Ethereum.

Yeah, I feel like cryptocurrencies only have a chance of providing value to some users if it's not actually very succesfull.

- If it's successful in providing anonymous transactions to everyone: Regulated to death due to laws aimed at combating money laundering and organized crimes. Even cryptocurrencies that aren't perfectly anonymous will probably eventually be regulated to death for not providing good enough guarantees about the identity of the wallet holders. - If it threatens the Eurodollar as a world reserve currency: regulated to death at least in USA and probably Europe.

In what scenario can cryptocurrencies actually achieve its goals without risking being regulated to death?

And yes, I know you can't effectively ban all trade of cryptocurrencies. But trade will always be a niche if most people can't use it in the real world.