Too much overseas flying?
I can see the problem this Captain and perhaps the F/O faced. Australia is the only country in the world that has such stringent 'visual descent at night' rules. In any other country in the world this would not have alarm bells ringing. When he had mentally planned for a visual approach and then heard the words 'approved' his confirmation bias and overseas experience took control and he took it as approval for an unrestricted descent. Pity that the F/O asked to talk to the pax and then the Capt unilaterally decided he was visual, informed ATC, sought approval for and executed a fairly non-standard sort of pattern in a jet aircraft at night to reposition. Had the F/O been involved in the decision making he might have had time to remind him of the visual circling at night rules. As it happened when the F/O rejoined the discussion he was then out of the loop and all the decision making had been made.
A good example of overseas experience causing problems for Australian aviators returning to Oz was in a sim session where a DME arrival was required with an overfly of the airport to land. Said Capt hadn't ever done one of these for real except decades ago in a light piston twin. He overflew the airport clean and configured on downwind and landed. Safe? Yes. In accordance with regulations? No-he should have been configured five miles at the final approach fix. Only in Australia.
Perhaps this captain was unfamiliar or vaguely aware of the visual circling at night rules.