The answer(s) to the title question are probably fairly obvious. Elon Musk is constructing hundreds of spy satellites for the United States for the money and because his company, SpaceX, now has a vast amount of experience in building satellites. SpaceX Starshield was awarded a $1.8 billion contract to do this in 2021. They've already successfully built and launched literally thousands of satellites. They've put so many into orbit that astronomers are complaining that he's messing up their long-exposure photographs. Perhaps the real question we should be asking is why we all know about it. Isn't that the sort of thing that you'd like to keep secret from the Russians and the Chinese? (NY Post)

SpaceX is developing a network of hundreds of spy satellites under a classified contract between billionaire Elon Musk’s space company and a U.S. intelligence agency, according to a report. 

The network is being built through SpaceX’s Starshield business unit as part of a $1.8 billion contract the company inked in 2021 with the National Reconnaissance Office, which manages spy satellites, five sources told Reuters.

The new spy system, which would feature hundreds of satellites with Earth-imaging capabilities that can operate as a swarm in low orbits, would provide the United States the most persistent, pervasive and rapid coverage of activities on Earth.

As it turns out, SpaceX has already launched up to a dozen of the Starshield spy satellites. That was part of a smaller, initial contract intended to provide the proof of concept required to gain the big contract that followed. It's not clear to me why that knowledge was made public either. Like it or not, we're engaged in a type of modern space race with both Russia and China. This seems like the kind of data you'd want to keep close to the vest.

Hiding these facts entirely may have been impossible for all I know. But it just seems as if the spy satellites could have hitched a ride on one of the Starlink launches and been dropped off in orbit with nobody being the wiser. SpaceX is launching so many rockets these days that it's hard to keep track of them all. They had 98 launches in 2023 and are shooting for 144 this year. There are currently more than 5,500 Starlink satellites in orbit. That has to be a tough job for the Chinese and Russian spooks to keep up with. 

The space race in question is already heating up. Just last month, China launched one of its Tongxin Jishu Shiyan-11 military satellites into geosynchronous orbit. They claim that it's only being used to "monitor communications," but they are clearly up to more than just that. It's a poorly kept secret that the Chinese have been working on methods to disrupt or even destroy the satellites of adversarial nations, including those of the United States. Meanwhile, Russia is taking a slightly more low-tech approach to the problem. They're simply blowing satellites up. 

We have become ever more reliant on satellite technology over the years, whether the public realizes it or not. We rely on it for everything from communications to conducting warfare. If someone starts blowing all of these birds out of the sky, we will be looking at significant setbacks that will impact nearly everyone in various ways. Just think about the way that most of us have come to rely on our vehicles constantly "knowing" where we are and being able to provide maps and instructions to reach our next destination. WIthout satellites, you might have to go back to learning how to read a paper map. Imagine the horror.