Espionage is typically conducted in secret. Snowden publicly released the documents and publicly announced his role as the leaker.
or if he is a very slick operative and this whole thing is part of a propaganda operation as he defects to China.
All I can say is he stole all kinds of classified documents, revealed some to cause an uproar in the US and paint himself as a hero, immediately flew to the one other super power in the worlds sphere of influence and started advertising he needs help and has a whole lot more documents that would be of keen interest to said super power