Who discovered what Columbus stumbled upon wasn't India at all but an entirely new content?

The realization that Christopher Columbus had not reached India but had instead encountered a new continent was primarily attributed to the Italian explorer Amerigo Vespucci. In the early 1500s, Vespucci participated in voyages to the New World and documented his findings, suggesting that the lands were part of a separate continent. His accounts, particularly those published in "Mundus Novus," gained widespread attention and contributed to the understanding that the Americas were distinct from Asia. Consequently, the name "America" was derived from Vespucci's first name.