Here’s an article about what they did. (Skip the fluff in first third, it does get down to details later.)
But what's weird, IMO, is that some of the shorter highrises like the Millennium Tower were approved to be built not anchored, but on pylons floating in the soil layer:
https://sf.curbed.com/2016/9/16/12945600/why-millennium-towe...
https://sf.curbed.com/2016/9/15/12930402/millennium-towner-s...
I mean, sure, as long as things are stable, the weight of the building will keep it in place. But I don't think anyone knows how the soft layer underneath most of SOMA will behave, when a big earthquake comes. People know it will undergo liquification, but by how much, and what will it do to buildings on "floating" foundations, that's not certain...
That the Millennium Tower is sinking asymmetrically doesn't necessarily mean the design was flawed, even in a high-risk earthquake zone. It could be flawed, but the very fact that it's sinking doesn't tell us that. It could merely be that out of the hundreds of towers constructed globally each year, Millennium Tower was the unlucky outlier which defied the otherwise carefully weighed odds.
[1] https://www.google.co.uk/maps/place/Millennium+Tower+San+Fra...
The sinking does seem like a concern and is no doubt related. It seems like someone underestimated how much foundation work would be needed on that building.
How does the front door work? Do they have steps down into the lobby now?
I'm pretty sure the building would have lost structural integrity from the force applied by gravity before the lean can reach 30 feet.
That's very rough of course. Many bad things could happen much earlier, such as unexpected forces causing structural damage.
Note also that the WTC didn't exactly "fall over". It collapsed on itself.
The WTC did not fall over.