Ok - if you were king of the world, would you prefer to be managing an outright challenge to your authority, or would you prefer to manage a convincing appearance of an outright challenge to your authority?
Either way that challenge - Assange here - will take a lot of people's effort and energy. The people have the power but they are being managed. He becomes an idol to some of those people considered rabble rousers by the governors. (For the religious, in your mind (temple) you have accepted a false idol - while you believe it to be true you will die for that idol every day.)
As a controlled opposition character, he may provide some truth - he has to be convincing - but he won't deliver. He is not really a challenge. If you have read 1984, he is 'Emmanuel Goldstein'.
Its the same story as Snowden. These characters (if they are even real people and not pastiches or CGI) are controlled opposition. They are acting a role - its a performance. They are intended to draw the sting from genuine people's discomfort and distress over the way our society is being managed downhill into tyranny, to take their well intentioned energy, and to waste it, so that nothing is achieved.
Governance is not just politics. It is also the media, the news and the culture. It may seem preposterous to you, but given enough time, money and inclination, it really is possible for people to run all these things. Its the reality that we live in.