It actually is credible that JSun hacked them. The exchanges trust Steemit Inc to help them transition to new hardforks. They have run scripts from Steemit Inc in the past in this exact way. If the scripts aren't transferring liquid funds, there is a very good chance they would not be blocked.

However, I'm with you. There is zero outrage from the exchanges. They are claiming to be hacked (and insolvent) and then providing no info on the hack and taking no action against the criminal @justinsunsteemit. They are full of shit. They just want to act like it wasn't their decision. Well played, dipshits.