It is a combination of factors, primarily including:
- Industrial Revolution
- Superior military technology
- Economic exploitation (resulting in a large wealth inequity betwen the West and other Powers
The first wave of colonialism was able to suceed as their opponents, the Aztec and Native American tribes were centuries back in their development, and were no match for the Europeans, armed with horses, siege weapons, steel armour and gunpowder.
As a result of their success, they had accumulated and pkundered a massive amount of wealth and displaced it, and redistributed it back to the colonizing country. The immense wealth funded a number of projects, including additional explorations, military technology, and most importantly, the Industrial Revolution, which only served to further enchance their capability to colonize more land from more sophisticated and better armed, established civilizations, rather than tribes.
In addition to this, Industrialization and the widespread exploitation of slave labour enabled them to build up their economies into mass-scale, industrial and modernized ones, which allowed the West, their headstart into economic growth and development, into the First-world nations they are today.
The cycle of prosperity which was instigated by the surplus capital, funded the process of industrialization, which in turn resulted in increased capital, which subsequently resulted in the development of more sophisticated technologies.
The new military capabilities unleashed by the Industrial Revolution, the declining power of the civilizations in the East (such as the Islamic World and China), and together with their aggressive colonialist practises, managed to crush their non-industrialized enemies and reduce them to subordinate colonies.
And centuries of economic exploitation have cemented the position of the West as the military and economic superpower of the world, and given it the prestigious place it has today in politics, economics, military power and influence.