Why are the Vikings not considered the pioneers of America?

In history, Columbus is considered to be the discoverer of America. However, about five hundred years before him, the Viking tribes had already reached the shores of North America (in the eastern regions of modern Canada) and even founded colonies there. But this fact was unknown to the world community for a long time, and only Scandinavia and Greenland knew about these lands. And this was scientifically proven only in the 1960s, when the remains of several Viking settlements were found in Canada (Newfoundland Peninsula).