Denisova cave has been known for about 150 years or so. Back in the 1970s, the Soviet Union sent some archaeologists out to see what was in the cave. They found some upper paleolithic stuff (e.g. like what the article is about), as well as some mousterian stuff (very weird this far north and east). They did excavations over the next couple of decades and eventually, some of the dating/sequencing technology improved to the point where it could actually be used on the cave artifacts. That's when they discovered denisovans and immediately made the cave one of the most important archaeological sites on the planet. There's been no lack of funding since.