On super yachts there’s large hatches to get tenders (dinghy) in and out like a garage. Some also have swim platform hatches. If any left open that’s really bad. The videos below also has a comment from someone who’s been in boats by the same company that says there’s a design flaw / feature with a different set of doors that are not for tenders but people (like patio doors) that could slide open when the boat helmed (rocked) in the water spout.
There’s a video of a large sailing yacht (45m, compared to Bayesian which was 56m IIRC) in New Zealand getting rocked over almost 90 deg in the linked videos as well, that really shows what’s possible in the power of a storm. That boat isn’t believed to have a lifting / folding keel, though, and righted itself right away.
Also, the mast of Bayesian was much taller than it should be for bragging rights essentially, which makes for more windage to push the boat over.