He definitely should have been locked up, but a double life sentence plus forty years without the possibility of parole for selling drugs on the internet seems like overkill

Sure, if "selling drugs on the internet" were his only crime.

I vaguely recall reading he (unsuccessfully) paid to assassinate people.

Edit:

Read it here https://www.wired.com/2015/04/silk-road-1/

  Later that day, DPR messaged Nob.

  DREAD: ok, so can you change the order to execute rather than torture?

  DREAD: he was on the inside for a while, and now that he’s been arrested, I’m afraid he’ll give up info.

That's part of the controversy, everyone vaguely recalls that but is unaware that those accusations weren't even brought to trial (https://freeross.org/uncharged-crimes/). He was convicted of money laundering, computer hacking, conspiracy to traffic fraudulent identity documents, and conspiracy to traffic narcotics by means of the Internet.

That was never proven, yet they used an unproven accusation in the case against him and nobody seemed to think that was an issue.