The elaborate cathedrals built by the Norse in Greenland (a relatively small population which probably never exceeded 25,000 in total in all locations) is yet another testimony to the high civilization they built.
It could have taken as little as a decade for them to collapse. The larger eastern settlement discovered that the western settlement had collapsed and carefully buried the dead sometime around 1415. In just a few short years thereafter, they suffered the same fate and there was nobody around to bury them.
Not long thereafter, the little ice age made it to their ancestral homeland of Iceland and brought widespread starvation and near collapse. It was only because of a massive change in diet to include copious amounts of fish that Iceland managed to survive.
Their surviving construction in Greenland isn’t too elaborate, it’s not unlikely that the timber construction was recycled for emigration vessels to get out, or burned on some long, cold night. AFAIK there’s just the one ruined church that survives, Hvalsey:
