How did this prosperity lead to the shifting of the balance of global power and influence from the eastern to western hemisphere?

 In many ways, the period of 1000 – 1500 C.E. was full of contradictions. One the one hand, the states of the eastern hemisphere were overran by nomadic invasions (most notably, those of the Mongols and the Turks) that led to the toppling of post-classical kingdoms, but gave rise to the Mongol and Ottoman empires. These empires have been mostly renowned for their brutality, but historians have also noted that they provided the foundations for increased trade and communications. In contrast to the invasions of the east, Western Europe experienced increased political stability that would serve as the stepping stones of global predominance. How did the rise of nomadic empires foster the ascent of trans-oceanic trade? What subsequent problems would come with this ascension? How did this prosperity lead to the shifting of the balance of global power and influence from the eastern to western hemisphere?

Chapter 19, and 21 Will send source