Why do so many of the biggest dinosaurs keep turning up in Patagonia

It's not a coincidence at this point. Argentinosaurus, Patagotitan, now Bicharracosaurus, all from the same corner of southern Argentina, mostly discovered by farmers who happened to be walking across their own land. I teach Earth sciences and my first instinct was that it's just the geology, the right formations exposed by the right erosion patterns. But then I started reading more and I'm not sure that fully explains it. Is Patagonia actually richer in giant sauropod fossils, or does it just look that way because researchers have focused there? There's also the question of whether local farmers are more likely to find and report fossils than people in other regions with similar geology, which seems like something that would skew any dataset. I'd genuinely like to know what the distribution of late Cretaceous titanosaur fossil sites looks like worldwide, and whether Patagonia's concentration is real or partly an artifact of where paleontologists have been spending their time.