Why colonization ended during the second age of European empire?

Some commentators identify three waves of European colonialism.

The three main countries in the first wave of European colonialism were Portugal, Spain and the early Ottoman Empire. The Portuguese started the long age of European colonisation with the conquest of Ceuta, Morocco in 1415, and the conquest and discovery of other African territories and islands, this would also start the movement known as the Age of Discoveries.

Explanation:

The historical phenomenon of colonization is one that stretches around the globe and across time. Ancient and medieval colonialism was practiced by the Phoenicians, the Greeks, and the crusaders, among others. Colonialism in the modern sense began with the "Age of Discovery", led by Portuguese, and then by the Spanish exploration of the Americas, the coasts of Africa, the Middle East, India and East Asia. The Portuguese and Spanish empires were the first global empires because they were the first to stretch across different continents, covering vast territories around the globe. Between 1580 and 1640, the two empires were both ruled by the Spanish monarchs in personal union. During the late 16th and 17th centuries, England, France and the Dutch Republic also established their own overseas empires, in direct competition with each other.