The success of European explorers and mercantile adventurers appeared unlikely at the start of the 15th century. Europe was a backward place, geographically hemmed in by the more sophisticated Muslim world. At the end of the 15th century, the Spanish and Portuguese had overcome eastern barriers by looking to the West and developing new technologies and ideas that would provide the basis of Atlantic exploration, colonization, and exploitation.
Before 1492, Vikings made temporary habitations in Vinland and Greenland, but climate change and opposition from indigenous "Skraelings" doomed their settlements.
Why didn't other Europeans follow suit immediately? Well, there were a lot of reasons why the other Europeans didn't follow suit immediately such as: domestic turmoil, disease, lack of technological capacity, religious rivalries that drew their attention to the Mediterranean rim, Black Death (around 1350 which wiped out nearly 75 million Europeans), and Islamic Ascendancy.
Islam spread to the Iberian Peninsula, what is now Spain, from the Middle East into Morocco after the death of the prophet Muhammad. The Moors (as the Muslims were called because they were from Morocco) helped the Iberians. The Moors helped provide clean and running water which led to better diets, literacy, science, scholarship, and standardized legal codes. However, religious conflict increased. The Catholic Church noticed that the Iberians were turning towards Islam through learning Arabic, dressing the same, going to the Moor's courts for disputes and got upset.
The Iberian Reconquista (711-1492) was a period of almost 800 years in the Middle Ages in which several Christian kingdoms of the Iberian Peninsula succeeded in retaking the Iberian Peninsula from the Muslim Al-Andalus province (what is now Andalusia). The Reconquista made Spain a military-driven society, which led to its unification in 1469. Hidalgos were knights and/or warriors who served the kings of the Iberian kingdoms and fought on La Frontera (the line between the Spanish holdings and the Moorish holdings, emblematized by cities under occupation) who developed a vicious method for taking places over. In 1270, the Iberian Peninsula was reconquered by the Catholic Church, although war still raged in Europe. From 1270-1492 was the Consolidation of Fragmented Iberian Kingdoms. Queen Isabella and King Ferdinand married to reunite the kingdoms of Castille and Argon to form modern Spain. After the Fall of Granada in 1492, Ferdinand and Isabella gained the Moorish treasury and could now finance their ambitions. Since Hidalgos only knew how to fight and wage war, the Spanish Crown had to figure out a way to get the decomissioned Hidalgoes out of Spain.
During this period, as well, were the Crusades (1095-1291) which were a series of religiously sanctioned military campaigns waged by much of Roman Catholic Europe, particularly the Holy Roman Empire and the Franks of France.
Because of the Crusades and other events in Christian Europe, officials there began to police others who they considered "deviant." Jews were expelled from England in 1290 during this time, almost all except those who were considered scholars, and the Moors were expelled in 1492 from the kingdom of Granada. During this time, Pope Adrian IV issued a papal bull which gave England permission to colonize Ireland.
The fragmentation of the Catholic Chruch going on during this era, such as criticisms, dissentsion, and internal disputes, led up to the Protestant Reformation. Before Martin Luther nailed his Ninety-Five Theses to the door of his church, those who practiced folk religions in Europe were persecuted for their heretical practices. Religious imerative added to exploration and colonization. Spain expelled the Jews and the Moors from the country because the Crown wanted to produce a totally Christian world.
Prince Henry the Navigator gathered Muslim and Jewish scholars to his school of navigation in Lisbon. Explorers, men of science, early modern cartographers, and mathematicians gather to develop navigational formulas to sail around the west coast of Africa. I took 83 years of trial and error before Vascao de Gama circumnavigated Africa in the 15th century. Because of this navigation school, first Portugal and then Spain saw the loss of a lot of young men. Many died trying to sail around the African coast trying to make a name for themselves. Portugal allied with African coastal kingdoms proved lucrative for all parties. This made maritime trade seem worth investing in and deep sea navigation seemed possible. Through this trade, slaves could be bought and sold along with various spices and other goods from places like China and India which were very valuable to Europeans.