Part of the reason for this was that the Spanish and Portuguese had a 'head start'. The Portuguese had already started to explore routes around Africa for the purpose of circumnavigating the Muslim monopoly on trade between East Asia and Europe, as well as to potentially look for allies against Muslim nations such as Morocco.

The Spanish simply went west hoping to land directly in China.

With the completion of the Reconquista in Iberia, there were few existential threats to the Iberians, freeing them to invest in exploration.

By contrast, the Hundred Years War and ensuing turmoil weakened the British and French crowns, preventing them from getting involved in colonisation until later.