Well, this guy was killed after exposing a massive conspiracy and even the official story is that he was assassinated - albeit by small time random crooks. Conversely, Seth Rich hasn't been shown to be involved in anything that might motivate someone to have him killed. The only evidence that he was involved in something, that I'm aware of, is a cryptic comment from Asange.

Surely it's good to be skeptical, but being so skeptical that you draw incorrect equivalences between Russia and the US may be taking things too far.