What a powerful, research-backed statement from a study that incorporated all the prior pertinent questions that science has grappled with for some time. This research is further believable, if very sad and tragic. If one looks at anti-colonial/postcolonial scholarship by scholars like Quijano, Mignolo, or Lugones, it's not "weird" at all—as geography researcher and professor Mark Maslin expresses below—that "The depopulation of the Americas may have inadvertently allowed the Europeans to dominate the world."
Albeit expressed differently from a critical geography and intersectional lens, this view of colonization is foundational to these scholars' thinking. For starters, I encourage you to read Quijano's, Coloniality of Power and Eurocentrism in Latin America to discover that this isn't so "weird" after all. It's simply insufficiently examined because of the profound Eurocentrism of our curriculum and teaching at all levels that is so diffuse, it's invisible, unseen. It's the air that we breathe.
That's why I and others advocate not only for Ethnic Studies, but against continuing ongoing colonization and mindsets that lack curiosity or open-mindedness about such matters.
A good thing happening today as a possible counter-weight—although we truly cannot turn back the clock of time and set Earth on a dramatically different course—is indigenous revival, together with an awakening ecological consciousness among so many. I know that my students are generally deeply concerned about the environment, particularly in light of so much recent devastation.
At play aren't simply these decisions, but a way of knowing that continues to be hostile to the Earth which in the long term spells death, destruction, and decay. Hence, we educate. We transform ourselves even as we transform our classrooms, teachers, and society, as a whole.