From what they showed and from the interviews during the red flag, it sounds like the marshals on the post just before did a really good job of getting the yellows out and communicating the sense of urgency to the drivers. Unfortunately the location being just after the flag and around a corner didn’t help and the marshal post before them weren’t flying a yellow (idk if that’s standard for Australian motorsport but for us a single yellow always precedes a double)

Yeah, it's a pretty tough situation imo. Especially when you speak about a track like Bathurst. There will always be some factors that are really hard to control. I just hope it's something they learn from.

The crash has gone viral on motorsports social media and now everyone is talking about it, including people without an understanding of the race and the track. I don't claim I have all of the understanding either, and in the end I'm also just some random trying to speak on it without first-hand experience lol.

I do think there were a few factors that at the very least

I did see a few marshals talk about it, with some differing opinions. But mostly on the same line that something could be improved. It also remains that these marshals are volunteers, which is also part of an ages old discussion within the motorsport community. They make long days at Bathurst, especially with the early start as well. They're also understaffed, trying their best. I think that's part of a bigger problem not solely this specific crash or track.

In 2018 a similar accident happened actually, where two cars crashed. Leaving an Audi sideways on the track. A few cars narrowly avoided the incident but a Mercedes managed to hit the car, ending the race early. The yellow flag was only waved after the Mercedes passed the marshal post which was long enough after the accident to have been waving it already.

I think light panels could've been helpful here. The distance between the post and the actual spin was so small. Like you said, double yellows should be preceded by single waved yellows at the post before -- at least under FIA rules.

I've seen some argue that if they threw a SC after the Zelger spin, and Zelger had continued people (fans) would've been mad that the race was unnecessarily neutralized. But I'm always firm on the opinion that something like that should not matter at all. It seems like a no-brainer, especially on a track like this to be cautious when a car is stranded like that.

I've also been told:

In Australia, the trackside marshals are not required to have fire training, and so you are only to bring extinguishers with you if you are confident in using them. There are dedicated fire marshals that manage fire response dotted around the circuit separate to the trackside marshals.

Which might explain why the fire response was also so slow and cautious.

Safety response might also be considered slow. I think it was about 90 seconds. Once again, that's also a thing of this track. So I don't think it was that bad in the end. However, the red flag was thrown quite late, should've been thrown immediately at the impact. It's unfortunate for Aron the only exit was straight onto the track. I think it was quite lucky the passing car actually stopped.