Who can tell me how why western europe colonized the entire world?

Answer 1

Christianity?

Answer 2

HOW was down to the use of superior military technology, methods,
and organisation. Superior transport and communication systems, especially by sea -this was supplemented in the nineteenth century by railroads and telegraph. A morale boosting belief that Western Civilisation and Christianity were better ways of life and that their benefits should be spread widely. Superior economic and manufacturing systems. Also many European states had an underclass receptive to the idea of creating a new home and life away from the Europe of the Emperors - this made it easy to get colonists for new lands. Such lands also provided outlets for younger members of the Upper Classes who would not have inherited the sort of family wealth that they were born into.
WHY was down to economic ideas current at the time to the effect that a states prosperity depended on having markets for its manufacturing and agricultural produce, and that the way to ensure these markets was to establish overseas colonies that were tied by trade links to the colonising country - in fact most colonising countries found that overseas colonies that needed protection were more trouble than they were really worth, which is why doctrines of Imperialism withered in the twentieth century.
However the results of the Imperial impulse has been to bring societies and cultures into closer contact with each other which should, if there is no nuclear holocaust, lead eventually to a working world community - that possibility is one of the impulses behind modern globalisation.

Answer 3

Because it was there for the taking.