While I’m not saying there was or is a conspiracy, nothing about a professional hit requires the police, reporters, and family members to be “in on it”. If he hadn’t told his family they wouldn’t know to cover anything up. If you were having him killed would you tell his family and hope they keep quiet about it?
Most conspiracy theories are utter tripe, and this one my be as well. But to say it is false because these other people would have to be involved is next level conspiracy theorizing.
Last I knew anyone hiring out or doing this job would tell as few as needed. Only two people would be needed to power this conspiracy — the one who hired the hit man and the hit man. Why would the cops and family be involved? After the exposure of the emails, why would the press be involved? That seems like a conspiracy theory about a conspiracy theory to me.