(Disclaimer: This is just personal knowledge from a casual observer and occasional passenger. I traveled cross-country by Amtrak a few times and loved it, and wanted to learn a bit about its history.)
Amtrak isn't quite the giant evil corporation in the sense that Amazon is. If anything, it's more of a dying relic propped up by sheer nostalgia. Congress keeps it on life support with small, occasional injections of funds. Its infrastructure and equipment aren't just obsolete, but dying, neglected by a nation who's almost entirely switched to automobiles and planes. Amtrak is a lifeline into the heartland, where many small towns have no other transit options.
But Amtrak is largely unprofitable outside of the Northeast Corridor, which runs up and down the East Coast and has fancy commuter trains for the rich businesspeople and politicians. The rest of its network runs on decades-old equipment and trains and barely keeps up with operating expenditures. It shares rail lines with freight trains, but is subordinate to them, so passengers have to wait any time a freight train wants the track.
It's stuck in a catch-22.
As a business, it can't turn a profit because, at current ticket prices, it is often slower and more expensive than flights -- not even considering the money lost due to time off of work. For shorter hauls, intercity buses are often quicker, cheaper, and have more time slots. It's not really a practical way to travel for most people in our economy except as a form of recreation, almost like a land cruise, or for small towns with no other options, or certain religious sects that don't drive (Mennonites). So it's not just a very profitable business thing to begin with.
So why don't we just nationalize it and run it as a national utility? We can't; it was specifically founded in the 70s to NOT be a government-run service. Nonetheless, in the decades since, it stays alive only because of government injections... yet it can't be directly run by the government.
So it's a private business that can't survive on its own, doesn't have enough capital to do anything differently, and can't go out of business because Congress keeps propping it up. It's literally just stuck on life support. The wiki on it is pretty interesting reading: https://en.wikipedia.org/wiki/Amtrak#Public_funding
Covid hit them pretty hard too and caused a lot of shutdowns. They have to negotiate with something like 20 different unions to keep operating, when they've already been unprofitable for decades. Biden gave them more money, but I think that just keeps the death spiral going for a bit longer rather than actually fixing anything.
Personally, I think the age of passenger rail is sadly behind us. A part of me wishes they could resurrect under a different model, maybe more like a fancy land-based cruise ship, with fun amenities on board, more sleeper cabins, things for young people (clubs, pubs, games, maybe even traveling concerts), whatever -- e.g. make the train its own destination. But that requires both the will to transform their service and the capital to do so, and they have neither. And so, for the foreseeable future, Congress keeps paying, and the train keeps a rollin'...