Well he was accused of rape, or, more accurately, sexual assault by other countries' definitions. Those charges have now been dropped, for what I can only assume "a preponderance of the evidence suggesting the defendant is permanently insanity".
But he may have committed other crimes in his attempt to flee the rape charge (not sure if 'failure to appear' is a crime in the UK, that differs by jurisdiction).
None of all that has anything to do with Wikileaks, by the way. A person's good deeds in one domain don't make him immune to criminal charges for unrelated matters. The idea that two average Swedish women are somehow recruited by the CIA to smear him with (rather weak) rape accusations is rather preposterous.
You're right when you say that one person's good deed in one domain don't make him immune to criminal charges for unrelated matters. However, Assange did not just did a 'good deed', he became a very high value political target and most of the time such people are protected from unrelated charges, since it is very easy to false flag them/burden them with bs to keep them from doing their job.
For example in France the president has partial immunity. The case of diplomatic immunity also comes to mind.
Yet we continue to go after whistle blowers and journalist instead of the ones who committed these crimes against humanity.