There is a construction technique where all floor slabs are formed and poured at ground level and then jacked up along columns to their final floor…Then they are anchored to the columns…don’t know if that was the case here…I suspect substandard concrete and/or foundation issues…
Lift-slab
Not the case here, but it probably did incorporate “post-tensioned” floors. That’s where a series of post-tensioning cables (called “strand”) are cast into the concrete, and then tensioned before the forms are removed and jumped to the next floor. This allows a thinner concrete deck for the same span.
There’s never one single cause with a catastrophic collapse like this. One big clue though is that owners were complaining of significant cracks in concrete elements (not clear if it was a precast wall or part of the cast-in-place structure), which might indicate movement of the building.
The fact that they had an engineer doing an evaluation should mean that we’ll eventually find out what went wrong, and allow building codes to be updated to address those issue.