> Bitcoin needs a huge factory. ETH2 needs a billion dollars. I feel like a billion dollars could probably buy the factory you're talking about.

What you don't get is what comes after that.

In PoS, once you invest a billion dollars, you're set for life. In PoW, you invest a billion dollars but still have to keep investing more and more in order to survive. If you're complacent, a new upstart miner with innovative technology could swoop in one day with 10x more efficient mining method (it could take many forms, such as a closed source bitcoin node that does things much more efficiently yet still fully follows the Bitcoin protocol, or it could be a closed source hardware that they don't sell outside of their own mining operations, like Apple does with their own chips) This way the PoW network as a whole will keep evolving because of competition. In a PoS network there is no competition once you invest the billion dollars and it's a complacent network compared to a PoW network where everyone is constantly competing and comes and goes (those who can't keep up will get left out and leave). If you join a PoS network where someone has a huge stake collectively, you're basically joining a feudalist society where you're being ruled by a king. If you join a PoW network you're being ruled by entities that keep competing to show their competency. it's like the presidential election is going on for every block.