Both want to keep the public in the dark about all the crappy things they've done and continue to do against your interests.
I'm sure they do. And Assange/WikiLeaks did do good in revealing some of the things that the US and others had got up to. The trouble is that Assange/WikiLeaks, unlike others who have discovered misdeeds, do not behave responsibility in how they publicise and curate information discovered. They didn't just reveal information regarding the documented misbehaviours; they also recklessly dumped everything they found onto the internet. Reasonable people can disagree where exactly the right of the state to keep sensitive details secret lies but few believe that it has none at all. The lack of any responsibility at all in the behaviour of WikiLeaks moves it from the clear blue sky of whistleblowers into the moral grey. I can't see a single justifiable reason for publishing the personal details of teen rape victims, or the home address of a man arrested for homosexuality in Saudi Arabia.
Thus for both of them, Assange being denied freedom, healthcare, dignity, etc, etc, is great. It serves to show others what happens to you if you oppose the government and try to tell the world what they're up to. They very much want us to know that if you expose govt abuses, you rot in jail, you lose. You lose everything. So you'd better not try to expose them; just let them get on with turning into a police state, slowly, incrementally, but surely.
Assange is not being denied healthcare. His freedom was restricted more by his choice to hide in an embassy to avoid a fair trial for rape than by anything governments have done to him. Remember it was only in 2019 that the extradition request was received. The time from 2012 to 2019 was entirely down to Assange. He cannot claim that the big mean government was oppressing him when he was hiding in a room entirely of his own volition and time in jail for skipping bail is just how it goes down.
I do have concerns about the same areas as you, I just don't agree that Assange and WikiLeaks are a particularly effective agents for change. Their irresponsibility undermines the good work that they do.
If you were given information by insiders in the US that told of war crimes, and you decided to expose it to the public, don't you think you'd be on the American government target list, that they would try to discredit you?
Usually when someone leaves a country on the same day charges against them are enacted then spends the best part of a decade hiding in a small room, all in order to avoid facing a fair trial for a crime in a country widely recognised to have a first class, independent, justice system one tends to conclude that this at least
points to a likelihood of guilt. And, frankly, I don't find the idea that the US somehow managed to turn two enthusiastic WikiLeaks supporters against Assange, persuaded them to make false allegations against him, then persuaded the Swedish government to press for extradition on these charges remotely credible. Especially when all this occurred at a time when the US wasn't making any attempt to extradite Assange themselves. But, since Assange has managed to avoid that fair trial through his actions we won't ever get to see whether the allegations against him stand up in court.
IIRC he wasn't the first person that Wikileaks asked to be their public face, but he may have been the one to have jumped at the chance without considering what it meant.
WikiLeaks was founded by Assange.