Earlier quoted context omitted.
No, he didn't. The prosecutor "addressed the jury and stated that none of the six contracted murders-for-hire occurred." These charges were dismissed with prejudice. https://en.wikipedia.org/wiki/Ross_Ulbricht#Silk_Road,_arres...
I think you are misreading that. They didn't "occur", because the hits weren't carried out. At least one, if not all the hits were contracted to an undercover FBI agent, which is how they caught him.
Do you have a citation for your undercover agent claim? I believe you're actually talking about DEA agent Carl Force and/or Shaun Bridges who were caught lying/stealing and charged with crimes [1].
1. https://www.dailydot.com/crime/silk-road-murder-charges-ross...