Well, the other possibility is that there isn't enough proof. But IMO if there isn't enough proof, he's not guilty, and they shouldn't even mention it, to avoid damaging his public perception.
The counterpoint to what you say is that the evidence comes from personal documents/conversations/etc. they obtained, and if they released some of that but not all -- in order to avoid publicly releasing any murder-for-hire bits -- you would be here saying that the selective release is suspicious and that they should release everything in order to avoid damaging his reputation through cherry-picking evidence.
