@HazelPlayer @MidnightLibraryCard I'm not sure why you're thinking a yacht would normally get anything close to 45• of heel at anchor - storm or not. Hold your phone in front of you at 90• to a table or something. Now tip it to 45•. 45• is a hell of an angle of heel. No-one would be able to stay in bed! The guest suites don't have pipe cots on a pulley system like offshore race boats, they're flat beds with luxury matresses (which, evidently, aren't currently required to be secured well enough to their bases on a superyacht).
Most monohulls would normally start putting reefs in to reduce sail area & make the boat heel less once they get to 25• or so. This boat in particular had some very strict rules about when to reduce sail area, to protect the structural integrity of the mast, so probably never heeled more than about 18• or so even when under sail at sea. The picture attached is her under full sail, reasonably close hauled, and I don't think that's even as much as 10• of heel she's carrying.
So having ventilation openings for running ac, as well as allowing the generators to run the ac, and the main engines to be flashed up would be a completely normal anchored condition. You'd really only close them when sailing - and that more for wave action than pure heel angle. (And yes, you do need to design to have ventilation for the main engines too - it's quite hard to burn diesel if there's no oxygen available.)
If you're interested in why the yacht is better off with the keel up at anchor than down, have a read of https://britanniapandi.com/2024/01/dragging-anchor-prevention/ As the wind blows at anchor, it tends to send a boat a bit sideways on to the wind as it pulls at the anchor rode. With a large fin keel down, this would present an angle of attack to the water, and the keel would essentially start making the boat 'sail' up towards the anchor (their figure 6 in link, but with additional lift from a long fin keel). This makes the anchor rode become slacker, then at the extreme end of this arc, windage takes over again & the boat is blown back downwind & the anchor rode loads back up. If this creates a large load difference, the anchor rode will 'snatch' as the load comes back on to it, which makes it far more likely the anchor will be pulled across the seabed. So having the keel down would probably make a yacht with that configuration far MORE likely to drag anchor.
The amount the boat heeled so quickly is most likely to have been a combination of an extreme down draft, then some kind of initial flooding and then free surface effect of water in the hull creating further heel (and then further flooding).
This was a sinking which has absolutely shocked the industry and has sailors all over the world scratching their heads about what happened to make the heel & amount of water taken on to sink happen SO quickly.
Like everyone else, I'm keen to understand what actually happened when the MAIB issue their final investigators report. Whether that will be in 8 or 18 months time who knows yet? If I was the owner, captain, or an MAIB investigator, I would certainly be keen to get as much photographic evidence as possible of the state of hatches, hull structures & appendages while she's still on the seabed though. Raising the hull in too much of a hurry risks loading it in a different way such that any existing cracks or damage may spread - essentially not preserving the 'crime scene'. I hope there will be enough resources at the investigators' disposal to assess the boat properly in situ now the primary objective of recovering those lost has been achieved.
There are a LOT of questions still to be answered. But why the ac vents were allowed to be open in an anchorage with c.40-50 knot winds forecast isn't really one of them.