Hard to know. One motive can simply be wanting to continue getting speaking slots and (possibly) speaking fees. Given his position, the public forgetting about him is a genuine danger to his life.

It's also likely that the Russian government has something to do with it. Bitcoin is not good for Russia if used internally. So having Snowden FUD Bitcoin privacy aligns with their interests, and it's not like Snowden can easily say no if told to say something. I've heard rumors that Ukraine is using Bitcoin to pay informants and saboteurs in Russia with Bitcoin, and I'm inclined to believe that is happening.