There has obviously been a lot of speculation about the cause or causes. Foundations in that area are usually very stable as they know the soil conditions quite well. I was interviewed by a local news team for my perspective on the failure. My first impression from the videos was a column or beam failure in the parking garage. This would likely have been a result of chloride intrusion and rebar deterioration.
I don't know if that was the cause, but that would be my first approach to a process of elimination.