From the FAQ, by /u/LoneGazebo, Is There Any Evidence That Moors Reached The Americas Before Columbus?:

when considering exploration, travel, trade and technology, one must always ask themselves, 'what would they have gained from this?' In other words, what was the motivation to explore? To give examples, what would Ottoman explorers, or even North African explorers, have gained, or have even imagined to have gained, from traveling west to get to India? The Ottomans, for example, dominated the East-West trade between Europe and Asia - circumventing their own trade monopoly would not have benefitted them in the slightest. The idea of 'exploration for the sake of exploration' does not emerge, in the context of the Atlantic World, until much later (if, debatably, at all). Even if Portuguese fishermen sailed into the Grand Banks, or Norse explorers to Newfoundland, the reality of their contact is, while historically fascinating, not terribly consequential in the grand narrative of the Atlantic World. Why? Because, until the early 16th century, the technology, and desire, to do something with this knowledge was unavailable. Even if the Norse knew what they had found, and wanted it, they lacked the demographics and economic infrastructure to effectively exploit their 'discovery.' Even if North Africans somehow managed to go to the Americas and back, the consequences of that contact are marginal at best. In short, we do not discuss Columbus, or 1492, as a consequence of his 'discovery' (more aptly, he 'ran into' the Americas), we discuss Columbus because Spain had the capacity, and the desire, to act upon his exploits. If Spain had not acted upon Columbus's dubious voyage to India (as he believed), that moment in history would have been as inconsequential as prior moments of contact.