Final answer:
Germanic rulers utilized Salic law to promote social order and inheritance, while Christian conversion was used for cultural unity and legitimizing rulership, not to suppress the church or establish absolute monarchs.
Step-by-step explanation:
The main reasons for Germanic rulers to use Salic law and Christian conversion were cultural unity across central Europe and ensuring that their successors would gain legitimate rule. Conversion to Christianity was not meant to suppress the power of the Roman Catholic Church but rather to integrate the Germanic rulers with the Roman populace. Furthermore, Salic law, which outlined a system for inheritance and governance, was used to ensure a smooth transition of power and promote social order. Christian conversion also legitimized the new rulers and helped tie the diverse subjects of these rulers into a more unified cultural and religious framework, facilitating the integration of Roman and Germanic traditions.