Possibly protection to himself. He already knew that series of development and progress of btc will be a threat level to some business and government. If you are the founder then likely you are at risk to some of these people. Also theres an cia scene that could result to a more complicated results connecting him. For me its a good riddance for him to stay hidden and totally anonymous for his safety too. Though everyone are eagerly wanted to meet and know him.
But we haven't heard any form of harassments from any agency toward those that have contributed to the growth of cryptos by developing other cryptocurrencies.
He's aware of the possibility that the government would track and attack him since he's the founder of the currency and they know that he owns lots of Bitcoin. His escape and hidden identity is actually very wise move because he could live peacefully without being bothered by anyone. Bitcoin's reputation and trust rate wouldn't be affected as well. That's just my view but he is the only one who knows his reason for bowing out of crypto what he did was a brilliant exit. His anonymity has a good impact and benefits Bitcoin as well as his life.