What we can analyze in these cases is that, if some crypto-coin can challenge the role of Bitcoin in terms of criminal use, it will be Monero (XMR) and Zcash (ZEC) because it certainly has more to offer to the curious who wish to operate with greater anonymity.
And that's fine. If people don't like Bitcoin because they think it's being used by criminals maybe this will change their mind. There are already coins that can do it better.
Europol I guess
You can't figure it out even with Bitcoin. You only have to remember to keep multiple wallets and never link them together in any way.
The most important thing is who you are not how much you have. If they get your name they will make you talk