Example [here](https://phys.org/news/2010-12-air-playstation-3s-supercomput...).
The hack allowed users to continue using them as such, though to what extent that persisted I don't actually know.
In the PS3 era, the PS3 had the highest compute power (FLOPS) to cost ratio of any commercially-available computer, due to a combination of its parallel architecture and the fact that Sony's business model was to sell the console at a loss and make up the money by taking shares of game revenue (and by charging $6 a month to allow the console to connect to the Internet)
But it turned out that it was possible to jailbreak the PS3 to run software other than certified PS3 games (this was officially allowed at first, but Sony quickly pulled the plug). And as a result, the best bang for your buck for "highly parallel we just need FLOPS" supercomputer workloads was to build a rack of PlayStation 3s.
But that only worked as long as the hack worked.
I recall exploits allowing some level of access to the RSX and other components Sony had locked away from OtherOS as far back as 2007, and Sony had already removed OtherOS from the PS3 Slim with no warning or explanation in August of 2009.
Geohot didn't even start on the PS3 until December of 2009. At that point Sony had already made it clear that they no longer saw value in OtherOS and wanted to get rid of it. Geohot's exploit (which was janky, required external hardware, and didn't even enable homebrew much less piracy) gave them a convenient excuse but there's no reason to believe they wouldn't have jumped on any other excuse.
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I do love how Sony immediately learned the hard way that there are a lot of very skilled people out there who are more than happy to play in a sandbox and not make a mess in the rest of the yard as long as it gives them enough room to do something interesting, but if you take the sandbox away they're going to play everywhere else.