What causes a building to collapse if it's not OBVIOUS like a tornado/sinkhole/explosion? Use of faulty building materials? Shoddy work?

Here's a horrific thing I found out today Walt. THAT building had been sinking since the 1990's allegedly. If they couldn't shore it up why didn't they tear it down? Don't you think that's beyond weird? Thank you for your reply! :)

I don't know about Florida ... but neither WA nor OR have building inspectors going around checking older buildings, unless something specific comes up.  (EG: a government push to retrofit buildings to newer earthquake standards)  

If the tenants complained loud enough, the city might send a safety inspector ... but they aren't structural engineers, and would have no idea if there were structural problems.

The whole thing seems very suspicious to me Walt. For decades the building was sinking. A known. Did they even try to save it structurally? How could something that was known to be going on FOR DECADES have been ignored like that? A structural engineer maybe could answer that? I sure can't. Thank you for your reply m'dear! :)