If I had to speculate, it is a calculated decision on WL's part to try and shift the organization's integrity away from Assange. Currently all trust in WL rests on Assange's existence which isn't good for the longevity of the org if/when he decides to retire (or meets his untimely demise).
WL has certainly been in a weird spot over the last few years, with nowhere near the straightforward anti-establishment reputation they pulled off in their Collateral Murder days. Assange's charges and sanctuary issues, Snowden's failure to partner with WL, the Appelbaum revelations, bizarre arguably-anti-Semitic tweets, and a suddenly-bipartisan-and-effective effort to cast them as anti-American.
I wouldn't be at all shocked if there's an attempt underway to quiet things down a bit and change focus. Without getting into the validity of any of the things pressing on them, there's certainly a lot of evidence that they're short on reputation and resources, and struggling to run successful PR, redact releases, etc. Moving away from Assange's centrality, and perhaps from the American focus, might give them some leeway to become a longer-term-player. Maybe.
Wouldn't that just prove that someone knows the private key of the signer? That's not sufficient to prove that the signer is alive.
Shouldn't we wait for the explaination he may come up with tomorrow on reddit? I just don't know on which channel this AMA will happen.
On Periscope he implied that it was done maliciously to discredit Wikileaks, I'm explaining how it was completely avoidable for them.
1) Julian disappeared completely after the internet to the Ecuadorean embassy was cut in October 2016
2) Wikileaks inexplicably changed their policy for insurance file hashes, publishing the hash of the decrypted files instead of the encrypted ones. This meant the hash of the insurance files didn't match the .AES files, giving the impression that they had been altered
3) Wikileaks stopped issuing verifiable proof of life for Assange. A simple PGP signed message would have sufficed.
With all that was going on, it was actually very believable that Assange had been abducted/killed during the internet blackout, and that Wikileaks was now being run as a black-ops site for a three letter agency.