Was it not here yet? What changed?

Edit: Ah. Better drilling techniques, ironically, pioneered by the fossil fuel industry!

Latimer and his colleagues improved on traditional geothermal techniques in several ways. But the biggest was this: They utilized horizontal drilling, boring about 10,000 feet down and then 5,000 feet to the side with each well. The technology has been around for decades, but it’s gotten a lot less expensive since the mid-2000s due to widespread adoption by oil and gas companies.

Nice that this drilling technology can be used in green energy applications too.