The murder for hire charges were dropped. No evidence of them was shown in court. Because they knew they couldn't win on that one.
First: as the appeal opinion clearly states, there's still an open case against Ulbricht for the Force-related murder-for-hire scheme in Maryland. The charges have not been dropped.
Second, evidence of the murder-for-hire charges was presented in court. It was an element of the conspiracy charge. Not only was it presented, but it was presented in a way that Ulbricht's defense was obligated to rebut it.
Finally, the murder charges were presented again during sentencing, and proven to a "preponderance of evidence" standard during that process as well.
These details are all spelled out in the appeals decision.
They've more than cleared that bar here.
For example: Is the rational that if I earnestly believed I was planning on murdering someone who I thought existed, that it is the lead up and consideration that is the crime, rather than the actual attempt (which could never happen)?