The guy should have gotten some time—not so much for the Silk Road itself—but, as I understand it, he was soliciting injury to one of his rivals.
However, life seemed a bit harsh.
There is a good article in Vanity Fair by Nick Bilton, who attended the trial.
He did cause some deaths with his drugs and poison smuggling. Some government agents involved with him went to jail.
The sentence may seem harsh but the article does explain why. He was offered, and declined, a plea deal that would have been appropriate. If Trump grants clemency he should also grant clemency to the black kid that was sentenced during the lunch break of the trial.
“The government also accused Ulbricht of paying for the murders of at least five people, but there is no evidence that the murders were actually carried out, and the accusations never became formal charges against Ulbricht.[48][49]”
- Wiki
Apparently, not enough evidence to charge and convict...