How does a building just collapse? Totally collapse. All at once? I’m not an engineer though.
reports from 2018 engineer survey noted structural damage below pool deck. This pool is not in ground. The outer structures of the pool sides are visible in the lower parking garage, as a wall, just like the hot tub.
Pool was reported to be continually needing repairs due to leaks.
Had the structure settled, as reported in the 90s and had that settling slightly cracked substructure parking garage, which is the entire footprint beneath the building (including the entire pool deck), the rebar and beams in the cement would be exposed to salt air. If the chlorine in the pool seeped into those cracks, the corrosion to the steel inside would have swollen the steel rebar and beams even faster, further cracking the cement.
The collapse appears to have begun in the substructure giving way and gravity doing the rest.