Much of what made the Iberian voyages of discovery was technology. There were a number of types of technology that helped allow this. For example, there was the caravel. This was a type of ship that could carry a relatively large amount of cargo while being maneuverable and able to sail fairly directly into the wind. Another example of technology that allowed these voyages was the astrolabe. This device helped people navigate more precisely because it allowed them to know where they were to a greater degree of precision.
There were other things that made these voyages possible. For example, Columbus's voyage was made possible in part by the ejection of the Moors from Iberia. This freed up resources for funding the voyages.