Final answer:
The Catholic Church granted the title of Holy Roman Emperor as a reflection of the political and religious unity of Western Europe under Christianity, intertwining the church's influence with the governance of European rulers.
Step-by-step explanation:
The Catholic Church granted the title of Holy Roman Emperor to kings primarily as a testament to the political and religious unity of Western Europe under Christianity. This title represented a significant political institution of the medieval period, emphasizing the intertwining of religious authority and European governance. It symbolized the church's influence in legitimizing rulers and bolstered the idea that the emperor's power was in concord with the spiritual authority of the church.
The Holy Roman Empire itself was a complex political entity composed of numerous principalities and a variety of rulers. Despite its name, the empire was not a continuation of the ancient Roman Empire but a separate entity that developed in the early medieval period. The empire's elected emperors held varying degrees of power and were often subject to the ecclesiastical authority of the Pope, epitomizing the profound entanglement of the church in secular affairs during this era.
In conclusion, the title of Holy Roman Emperor underscores the influence of Catholicism in European politics and the tradition of an emperor being elected by principalities and crowned by the Pope, reaffirming the church's central role in both religious and temporal realms.