What happened is clear not least because of the video. Why it happened is less so. As an experienced captain on type I would venture a few comments. At first sight the crew were qualified and in terms of total flight time very experienced. However there was quite a marked cockpit gradient. What I mean by this is that the Australian co-pilot only had a few hundred hours on type while the local captain had 19,000 hours total time. This would not be the first time that a junior pilot was slow to speak up. Interestingly about 15,000 of the captain's hours appear to have been as co-pilot, which in a hiring interview would at least raise questions. Based on his performance on this and the previous flight we might reasonably speculate as to the reason why. The co-pilot did make the very reasonable suggestion that flaps 40 would be a good idea. With a potentially wet runway just over 1800 metres in length it is surprising that the captain was planning for anything else.
The 737 on a normal day is a very easy airplane to fly. With a short runway and a non precision approach in poor weather it needs another level of skill. The reconstruction shows very well the initial approach as just another day at the office. Bit of weather ahead, but the captain says they will break out in time, which is a pretty clear case of confirmation bias. If he had asked the co-pilot what he thought and whether they should hold for the weather to move away, he might well have got a different answer. Precisely because flying has become so routine there is a great tendency to continue. Doing something different is much less comfortable than just carrying on even with sink rate warnings etc. Alarmingly this is one of several very similar events I can think of with the 737. The Bali crash and the St Maarten Westjet event are two obvious examples. A particular issue is a high mda where you decide to continue and as per Boeing procedures click off the autopilot and autothrottle. At this point when you lose sight of the runway your actions should be clear, go-around. Flying a light aircraft you add power and in this case turn left towards the missed approach. In the Boeing you are in much less familiar territory and doing something many people very rarely do in real life, flying the aircraft without guidance or automatics.
There are of course many honourable exceptions to the rule. But as instructors know the weak pilots are the last ones to want to demonstrate their weaknesses and practice on line, even if the company allows it, which is of course another issue. There are a surprising number of large airlines who discourage switching off some or all of the automatics. The high cost of simulator time also means that these skills are often not the focus of valuable checking time. I would suggest that there would be a good market for a lower cost simulation alternative where manual flight could be regularly practised to achieve true competence on a regular basis.