Dang. Not just a failure, but a total failure of the entire bottom of the pool.
We’ll never get the rest of the story, but my bet is that the building operator knew that the pool was leaking, probably for years. The original engineering design was probably fine, but corrosion (and the third-world tradition of skimping on the rebar) led to a sudden tensile failure. An insufficient design, with way too little rebar should have lead to a plastic failure, much earlier in the structure’s service life.
Look closer - it wasn’t the bottom of the pool that failed. The pool appeared to be side-anchored, structural stability was based on side hangers ... there was no bottom support.