- according to two recent independent structural model calculations based on the original plans, the building that collapsed was deliberately designed to meet only 100% to 115% of the original static loads to save money, but not the dynamic loads of rolling vehicles or interior upgrades like granite counter tops and marble wall displays.
Also, there were a few 12" columns, no column caps, and not enough shear wall areas or elevator core tie-in to resist twisting from wind loads or prevent domino column failures.
- any number of events could have started the collapse because there was no safety margin, including water intrusion and previous hurricane wind loads, but it was probably vehicles rolling around the lobby level near the pool.
To answer your question, it would cost more than the building was worth to replace the columns and slabs. The 40-year review for that building really meant a teardown had they redone the structural model. The owners were already looking at a $100,000 to $200,000 bill each for cosmetic repairs. Because of absentee owners (lessors and airbnb), that level of investment for a rebuild doesn't fly.
It's believed that the former building inspector gave a positive building review speech so that cronies could continue selling units, as negative news would have to be reported to potential buyers, killing any sales.
Note that builders who looked at the post-collapse photos even one day afterwards all wrote, "Nothing looks right in those fotos." What bothered them the most were the columns that punched through with no debris stuck to the top (pejoratively called "those toothpicks"), and yards of rebar bundles that also looked too clean.