Most of the early members of wikileaks left before the first leaks pertaining to the US. Wikileaks original focus was to expose authoritarian governments in the Middle East, ex Soviet block, and primarily China's actions in Tibet. John Young, one of the founders actually left the group after accusing Assange of being a CIA plant after Assange wanted to do a multimillion fund raising drive.
The largest group to leave was before the 2010 Iraq leak, when the actual journalist at wikileaks warned Assange that the batches had not been properly redacted, and he published them anyway.
Fear for their source's safety actually led wikileak's security team to steal data from wikileaks and keep the data encrypted until Assange agreed to improve opsec. Assange ended up kicking them off the team, and they ended up having to delete the data.
I would really suggest reading what his early colleagues thought about his work, it really gives a lot of perspective about how poorly wikileaks was actually run, and how shady of a character Assange is.
Again, I'm not condoning life in prison. I just don't think he's the titan of ethics and moral integrity that people make him out to be. And he shouldn't be immune to prosecution for the unethical and illegal activities he committed outside the scope of legitimate journalism.