They were one of the two companies which managed to produce dedicated integrated circuits - so called ASICs. ICs are blazingly fast, because they have only one

They were one of the two companies which managed to produce dedicated integrated circuits - so called ASICs. ICs are blazingly fast, because they have only one purpose - to compute SHA2 / to mine bitcoins. There is no overhead that processors & GPUs had. A production of the IC costs high hundreds of thousands of dollars, and requires a ton of domain-specific knowledge. But once they're produced, each batch is quite inexpensive, and is capable of quite fast. Of course there could be other startups doing the same thing, but you'd need an around a million dollar budget. Not easy.