There are at least two reasons for the State to arrest someone. To seek justice or to create a political spectacle. Arresting a serial killer is an example of seeking justice. Arresting a young Adolf Hitler is an example of political spectacle. That arrest made Hitler who he turned out to be. No arrest, no spectacle, no Third Reich.
Sure Julian has violated a slew of laws. But none of those laws is worth the embarrassment that might ensue from a public trial. This is probably why Ecuador hasn’t been arm-twisted into releasing him. Trust me, if the government wanted him poor little Ecuador would be twisted around like Judo dummy. He isn’t worth the trouble and he has his value, like now.
When intelligence groups need to reach a large audience with perfectly laundered stories, they will dump them on him and he will dutifully publish them. The more outrageous the more people will believe them.
The problem with any intelligence is its provenance; where it originates.
If somebody wanted Julian dead all they’d have to do is send him documents allegedly hacked from Putin, or the Ayatollah. He wouldn’t live a month if he published them.
Of course he isn’t dumb enough to publish anything that might get him killed or really rile the US.
He may have wide range of clientele who value his role. Two mutually hostile groups may use him as useful conduit. So if one of them wants to take him down, the other may feel that it would be in their interest to protect him. He has to keep some balancing act, by trying not to appear to overtly take side.
He may not have started out this way, but along the way, some survival strategy of his own could develop. Anyway he is playing very useful role now. Nobody is perfect and everybody has their own agenda which may temporarily coincide with somebody else, who in different circumstances would be his enemies.
I don't think anybody is perfectly in control of him to serve their agenda. He may not be really in anybody's pocket. Spooks may want to use him, but not from one side. Spooks from mutually hostile countries.