We don't.
Seth Rich being alive actually explains the weird behavior of the family, friends, police, and everyone else better than anything.
I know of no other reason THAT many people would be so willing to cover up an assassination.
Come on.
It would be HUGE news.
It would destroy HRC, Obama admin, and the muh Russia investigation.
Someone would have come forward anonymously to the right person in the press or the Trump admin to expose this all.
I don't buy that EVERYONE connected to this is simply scared shitless.