Hey Howard Roark the Millennium Tower SFO, why is a newly constructed Modern Condo Tower in one of America's Premier Cities sinking into the Bay?
Commies!
OK, I am going to guess you don't know a lot about geology and that you are not a geologist like I am. The entire eastern and northern fringes of San Francisco used to be a coastal marsh but in the 19th, in order to reclaim land and to create deeper water moorings for ships, the filled those swampy marshes in using a combination of literally dumping garbage and waste into the marshes as well as "hydrologic fill" which means they dredged mud up from dealer in the bay and sprayed the slurry or mud and water into the marshes filling them up and slowly turning them I to dry land. Those units are collectively know as "bay fill" and they are both man made and poorly consolidated.
They are highly vulnerable to liquefaction in earthquakes and are a pretty terrible material to build on top of. Now, I don't know the specifics of that particular tower, other than 2-3 articles I have read in the popular media, but I can think of several possibilities as to why it would be sinking and most involve corner cutting or miscalcations wrt the number of foundation pylons, their sizes, and how deep they should go before determining they have reached "firm competitent ground". Setting those foundations up correctly is key but also extremely expensive to do right while developers often want to save money and argue cheaper methods would suffice. It gets even more complicated when local politicians (who often have their own agendas ranging from desire to be seen as delivering on big projects to outright corruption) get involved and start granting code variance permission. I can tell you some good stories about that sort of stuff.