There's a decent probability that the foundation was swallowed by a sinkhole. It's always been an issue here on the beach since it's an artificial island. It's never been a huuuuge problem, it's mostly just the roads that suffer, or buildings that are in sensitive areas where they skimped on the foundation.
I've just found a great explanation of the issues, for anyone with a bit of Engineering knowledge this is pretty clear
https://www.nytimes.com/interactive/2021/09/01/us/miami-building-collapse.html
it's behind a paywall, I used Firefox extension https://addons.mozilla.org/en-GB/firefox/addon/bypass-paywalls-clean/reviews/ to bypass
it's an interactive presentation, just scroll down
(post is archived)