Because he stood up to a corrupt legal system.
While he might be a criminal, he is seen as a hero for this reason.
Same as the people at the Eureka Stockade.
Gains are not always gotten nicely/legally, there were and still are people who have ill gotten gains, and it is only when someone stands up to them that they can be brought down.
So, in his case, at times, he was legitimately a criminal, and others, illegitimately a criminal.
As a question, do you see those from the French Revolution as criminals?
It is not always black and white.