Excessive groundwater extraction and urban development could be reasons for this. But these are common practice in almost all of the modern world, so why is this only showing up in Mexico City.
Mexico city was built on top a dried lake. It is really fascinating stuff, I would highly recommend to look it up. Ancient farming technology, floating islands, any nerd is gonna love it.
It’s not only Mexico City. This is happening in Jakarta, the Central Valley of California, Beijing, really anywhere with excessive groundwater extraction.
It is just most people pay attention to CDMX because it is a very large 20M+ city with a lot of American and European tourists, and it is happening quickly to the point where you can see it with the naked eye.
Mexico City (Tenochtitlan) used to be a city build on a lake, partly on an island, partly on some kind of static rafts / floatting gardens (chinampas).
You can see evidence of subsidence in the rest of the developed world as well: SAR interferometry is sensitive enough to pick up the minimal amount of building movement from building Crossrail in London. It's just this article focuses on Mexico City, where it's dramatic
There must be other contributing factors too.