Because no one was murdered. He tried to hire a hitman but the hitman ended up being an undercover FBI agent.

Don't defend this man, he is manipulative human garbage.

Was the hitman really an undercover agent? I though it was just someone scamming Ross for as much $ as possible.

redandwhite was almost certainly a scammer and got paid to kill friendlychemist and tony76 + three roommates. Nob was an undercover agent who got paid to kill "The Employee" aka flush aka cronicpain aka Curtis Green. Two different incidences.

he will be in another trial

Put him away for the things that are an easy conviction, rather than the more nebulous details of that attempt. Why cloud things?

Not sure why this is being down voted.

Of the two sets of charges, one was a much more easy conviction - the drug dealing.

It's not the prosecutor's job to introduce clouds of doubt into a prosecution. And this is not a case of "better ten guilty men go free than one innocent man be found guilty". He was, apparently quite overwhelmingly guilty of the charges related to running Silk Road. Why risk a conviction by charging him with something that might not stick (yes, I realize you can be found guilty of some charges and not others, but a whole world of doubt is introduced)?

Despite what others are saying about why he was not charged with these crimes, the real reason is because he is being indicted with these crimes, federally, in Maryland on those charges. He will face that trial next.

Now, to be fair, these allegations (not lies, allegations) could be just that. Allegations. The prosecution will need to prove them to get a conviction. The reason he is facing these separately could be that these attempted murder of a federal witness charges are much harder to prove and thus convict on.