Until the age of exploration Europeans played a nominal roll and trade why was colonization so important to them?

There is an important difference between the colonial activities in the Americas in that period of time and the European settlements elsewhere in the world. It was only Spain and Portugal that set up colonies in the Americas then, and their motivation was mostly 'gold'. In order to get to the gold, they had to effectively control those lands, because the local population would not of course willingly start up mines and do backbreaking work there just to help the Spaniards get rich.

In the East it was different: growing and trading spices was a long-established tradition there, and the Europeans just set up trading posts and made deals with local rulers with the aim to corner those local markets.

Colonization in the sense of taking control of countries in Asia and Africa was a thing of a much later age. That 'colonial period' in those cases almost never lasted longer than the period between 1880 and 1960.