Right well, if you're connecting IP addresses with known identities that's just not very smart :D
How hard can it be to hack a random WIFI when millions of dollars is on the line? How hard can it be to get internet access without revealing your own identity? What about VPNs and IP spoofing? Bouncing signals all over the world and making their job way harder? Bitcoin transaction can be airgrapped through QR codes, created with sound, and even broadcast with emoticons or radio waves.
The ability to decentralize ownership and identity is pretty easy if you know what you're doing. A lot of criminals are lazy, ignorant, or greedy.
Mafia organizations that scale big enough have agents within law enforcement. We're made to think that these "kingpins" are being taken out by law enforcement. Ross Ulbricht was no mafia kingpin, he was just a programmer libertarian dork that believed in free market. If he had been willing to go all the way and full-on create a mafia organization he would not be in jail right now.
As soon as Silk Road gets taken out it immediately get rebooted under new leadership. How does no one come to the obvious conclusion that these people they are arresting are not at the top of the pyramid?