To reduce it to its absolute basics, TNZ thought the young inexperience guys (the B team) couldn't foot to with the older experienced guns (the A team).
Consequently the team tried to neutralise this advantage by designing/building something at the extreme edge.
This was pretty much my impression.
Way I see/understand it: Apparently at least one team cottoned on to what was being done with hula & put a lot of pressure on via Measurement Committee who had previously ruled it legal.
TNZ were forced to put a lot of work & mental effort to prove legality.
Wound up having to make the gap wider, stiffen the hull & remove some sort of gel they had been putting in the gap to smooth the flow.
All that cost them some effectiveness of the hula + really hurt their actual sailing testing.
In all the boat was heavily optimised to maximising effective length/prismatic coefficient. As well as the hula it had a more extreme bow knuckle than before and the wickedly long bulb which will have also increased the prismatic.
But it will have had a significant effect on pitching moment too, I think stiffer initially for dealing with chop but once moving will have produced more violent pitch than shorter bulb.
Also lower CoG than fatter bulbs.
IACC rule had a sail area penalty for length so they either were effectively a longer hull & a sail area penalty or they used the tricks to make a boat with similar effective length but bigger sail area.
Also they had a thing with loading up a couple of sail bags in the stern scoop to alter the actual waterline in a way not caught by Measurement. Basically a cheat.
The structural issues are said to have started with the boat falling off a crest into a big hole, making a very loud crack, obvious damage & boat needed a lot of structural work to fix. (also added weight)
Then they were light on spares, were not sure about the structure so were pretty tentative in testing.
Clearly a bunch of stuff was at very light weight end of the structural spectrum eg the boom & spinaker pole -> quite possibly main structure was also very at edge too.
If I recall correctly the very long bulb was tested on the non broken boat & only switched to the primary boat for the AC -> final config hadn't been well tested.
Then on the first beat the water was coming in over the scoop/rear cockpit sides filling the boat. (Which was never fully fixed despite taking the sail bags out & putting screens in place)
The way I see it, the unexpected water plus untested fore-aft motion caused by the long bulb plus extra weight from structure caused a series of failures with various bits with fine safety margins not being up to the load.
And then even when stuff didn't break the boat still wasn't fast enough to make up for any shortcoming in boat handling sailing vs RC & BB at their peak in a fast boat they were comfortable with.