The most likely cause of the collapse of the Condo in Florida is the cement used to build this building

What happens is builder's sometimes want to save money so they reduce the amount of cement in relation to the sand. This weakens the cement to the point where over time something like this could happen. So, if it isn't some kind of terrorism or bomb or something like that the weakened cement from not having enough cement in relation to the sand used for making it could cause something like this. Even the amount of rocks used in the cement if it was not enough could cause a weakening of the cement too. One of my best friends worked as a Stone mason during the 1970s and 1980s too so this also contributes to my knowledge about this kind of thing.

In California something like this is much less likely to happen because our building codes had to be strengthened so much because of so many fatal earthquakes (especially before the year 2000) starting with the 1906 Earthquake that literally broke all windows in San Francisco and killed over 3000 people then. The evangelical movement sprang directly from this earthquake in San Francisco by the way because someone predicted it in the evangelical community before it happened.

But, generally speaking we have such strict building codes especially places like San Francisco, Los Angeles and San Diego because of past earthquakes that something like this is very unlikely to happen most places in California because of our very strict building codes. 

The other problem that could have caused this is the metal supports within the cement like Rebar in the way it was designed was not sufficient to carry the weight over time and so at one point this metal failed because it wasn't enough to carry this weight any longer so it created a chain reaction collapse of the building possibly when too many people gathered or danced or something like this on a top floor.

There are many buildings in China built by corrupt builders that people will not live in at all that are high rise apartments because they know these buildings could collapse because they know the cement and design isn't safe to be in. It's the problem of what happens when you have state run capitalism run amok in a country: People die as a result of the corruption in terrible ways.