In Directair's case, I don't believe that CASA had anything at all to do with why their doors are shut.
Something about "stop credit" with the refueller and can't (won't) pay the staff probably indicates more the reason behind their (possible) demise...
On the face of it, the verdict on CASA for Directair would appear to be "Not guilty, your Honour...".
However, I have read in depth about Directair's recent challenges in the Court regarding charter vs RPT, but that has been asked and answered by those charged with making our laws. I fail to see how CASA could possibly have acted based on commercial issues with that, or any other, Directair issue.
You are right, though - CASA's primary role is to act in the interests of air safety (this is enshrined in the Civil Aviation Act) - but there may be a whole litany of self-identified "secondary" roles, as we have seen over the years!!