We can point on several aspects, but the exploration of the New World and the dominance of the seas were among the main reason.
Explanation:
Portugal and Spain were the first to achieve the dominance of part of the world, but in the 16th century, after a long period of wars and political conflicts, England began its race for global dominance. However, the main part of the Globe was in the hands of Spain, specifically parts of America where Great Britain wanted to settle, and create a zone of influence.