There were probably many such explorations that never went anywhere that we do not know about. The Vikings discovery did not go anywhere and does not lessen Columbus’ impact.
Columbus was not even aware of the Vikings’ work and independently discovered America. Columbus’ work resulted in significant colonization and interactions between separate regions of the world and ultimately ... the birth of a new country.
The way I’ve heard it is “once Columbus discovered it, it stayed discovered.”
We also don’t know how many vikings made the crossing,
never to return.