Nothing happened to them, they're still around; just consolidated into industrial operations.

The "twist" is they rot as e-waste every 18 months when newer models arrive, generating roughly 30,000 metric tonnes of eWaste annually[0] with no recycling programmes from manufacturers (like Bitmain)... which is comparable to the entire country of the Netherlands.

Turns out the decentralised currency for the people is also an environmental disaster built on planned obsolescence. Who knew.

[0]: https://www.sciencedirect.com/science/article/abs/pii/S09213...