It is a technological marvel, similar in comparison to designing and building an F-35 fighter jet or anything else.
It requires custom Hardware Accelerators designed at a chip level, on top of decades of algorithmic refining of video encoder decoders in stuff like gstreamer or ffmpeg, refining video streaming at inconsistent cellular data networks, various ISPs doing shenanigans with ports, etc. Storing and ingesting that much video data at "Free" initial pricing, streaming that much data to viewers, building analytics algorithms to pair advertisements with watchers, to get a high enough conversion rate to make ads economically viable enough while having minimal number of ads per vids.
Even an infinite money printer like google would struggle were it not for systematically solving technology at all levels from hardware, to chip design, to algorithms, to network level tuning, to frontend device optimizations, etc.
And has been made possible by only the cumulative effort of humankind to build such advanced sophisticated systems in the palm of our devices such that even a normie average iphone 16e has more compute capacity than early 1990s or so, much more.
It is a miracle, in every shape and form.
It's also a massive attention sink that burns both copious amounts of energy and the world's attention span to earn some clicks and ad dollars.
It's a mixed bag.
That's why I question whether it's actually a "miracle". I don't mean to suggest that it's not quite the feat to make something like that exist, but I see it as more of a representation of where we're at technologically, rather than some sort of improbable, inexplicable thing that otherwise shouldn't be. The fact that the response to my post seems to clearly understand how it exists kinda-sorta supports that, IMO - you can draw a clear path towards understanding how it came to be.