I can't say I know every detail of the case but I don't recall anyone getting killed or even hurt by Mr. Ulbricht so in my mind the punishment does not fit the crime. IMHO the death penalty should be off the table completely (go Nebraska!) and life in prison reserved for only violent offenders. You can argue that he enabled people to harm themselves but I think that's stretching it. If people want to take drugs, even take too much drugs their going to get it somewhere. If drugs were legal and treatment of abuse the focus instead of punishment Silk Road wouldn't have existed in the first place.
The prosecution brought this up at trial but he was not charged or convicted of this in the criminal trial.
As an aside, you conveniently neglect to mention that Curtis Green feared Ross would have him killed simply because Curtis had been arrested and Ross knew that he might spill the beans. And since Curtis knows Ross better than you or I do, and the fact that he managed to predict that Ross would try to have him killed, brings into question whether the money really made a difference.