A very quick scan of Dr. Hawkes entry on Wikipedia suggests to me that he is a very experienced "safe pair of hands", a Mandarins mandarin, to put it another way, with long experience of cleaning out Augean stables.
I fail to understand why he has allowed CASA to deteriorate, in the industry's perception at least, to the point where he has had to cop the Truss review findings, it must be a shock to his system, assuming he is not a raving narcissist who rejects the entire review findings, which I doubt.
The question I would expect the Minister is still asking is exactly who wants to be part of the team to clean up this mess and if they have the qualifications for the job? No one who can read between the lines would underestimate the amount of work and risk to individual careers that the DAS role or a Board appointment would entail.
Even if the Board and DAS earnestly apply themselves to reform, they commit career suicide if there is a major accident before:
(a) A favourable FAA/ICAO review is achieved.
(b) Industry metrics show acceptable performance (note: I don't believe CASA or ASA have even signed up to any international benchmarking process).
(c) Regulatory reform is in place and hitting demonstrable targets.
(d) Industry surveys show an indisputably significant increase in the strength of relationships with the regulator.
...and (e) Ahem, regular favourable comment on Pprune and the more distinguished parts of the aviation press.
There are probably another half dozen outcomes to be added to this list.
Dr. Hawke? I expect he is stuck with the Chairmanship until it pleases the Minister to release him.
To put that another way, I think the Minister is still looking for candidates who are game to clean up the place and perhaps finding there aren't many takers.