I think it’s because he took/leaked confidential documents belonging to the ATO. This isn’t covered by the public information disclosure laws. You do not need to collect evidence, that’s up to the investigators, you are encouraged to provide your own records eg notes, journals.
As a backdrop, Australia is among the top 10 least corrupt countries in the world.
The QLD Crime and Corruption Commission website has many examples of the kind of corruption they find. It’s mostly to do with procurement and employment fraud, conflicts of interest, occasional dodgy police and major crime ie organised crime.
It is true the CCC is grossly under resourced and in need of reform, however as with many anti-corruption bodies, they become politicised and in this case the state government (either persuasion) is dragging the chain.
Yet to be decided, November 5th is the supreme court hearing date.
https://theconversation.com/trumps-tariffs-are-headed-to-the-us-supreme-court-prolonging-the-chaos-on-trade-264249
https://www.theguardian.com/us-news/2025/sep/18/supreme-court-trump-tariffs