At approximately 5:45 am on 16 May 1968, resident Ivy Hodge went into her kitchen in flat 90, a corner flat on the 18th floor of the building, and lit a match to light the gas stove for a cup of tea. The match sparked a gas explosion that blew out the load-bearing flank walls, which had been supporting the four flats above. It is believed that the weaknesses were in the joints connecting the vertical walls to the floor slabs. The flank walls fell away, leaving the floors above unsupported and causing the progressive collapse of the south-east corner of the building. Source
One issue with pre-cast concrete slab construction involves the joining of one slab to its neighbors. Robust construction requires that surrounding structure be integrated enough that the load carried by one element can be carried by its neighbors in the event one of them fail. Poor integration means that load cannot be diverted to the neighboring structural elements.
Incidentally, John D. McDonald wrote a superb book titled Condominium. Yep, the condo building collapsed in the story with a little bit of help from a hurricane. One of the contributing factors was that the pilings were not a continuous pour as required by code and best practice. Frequent downpours resulted in silt washing into the borehole covering the exposed surface from the interrupted pour which then prevented the next pour from adhering to it
I suspect good old John D (famous for his Travis McGee series) did research and asked construction guys "What are the most glaring examples of bad practice you see in the construction of Florida condos?"
When everybody is building it is difficult for suppliers to meet the demand and interrupted pours happen.