The way I have heard it is “once Columbus discovered it, it stayed discovered.”
It was through Columbus that knowledge of the Americas reached the wider world. All the Norse did was “discover” that there was more land to the west of Greenland, and this fact was soon forgotten and never acted on. The information never got to the wider world.
Quite so. Columbus established a lasting connection that led to European settlement and development of the New World and the rise of a global human civilization.