I have this feeling that they were doing some construction work on the roof and that may have triggered an event that cause structural members—weakened by all the salt air over the years—to collapse suddenly.
Salt air and proximity to the beach cannot be the complete answer. There are quite a few large poured concrete hotels right on the beach in Miami which were built in the ‘30s, The Ritz, The Delano, and The National, among others. Before being renovated in the ‘90s, they survived decades of extreme neglect, dilapidation, and even hurricanes without collapsing
It’s highly coincidental