Question

Why was the Roman Catholic Church so powerful in Europe during the Middle Ages?

Answer 1

When it comes to the Catholic Church during the Middle Ages, we should mention the close connection between the Church and the empire as well as  the monarch. This created a political connection between the Church and the rulers, where mutual help and support were provided. In the absence of new ideas that would confront such a combination, until the appearance of the Renaissance, this political tie was very effective in its domination. In addition to the Catholic Church, there was also the Orthodox Church which had a similar concept. The clergy played an important role in spreading and strengthening church learning, with effective methods to prevent any "heresy". The Church had great economic power and wealth and played a decisive role in making political decisions. The rulers, on the other hand, benefited because the Church secured their legitimacy through the idea of ​​a divine ruler established under the patronage of the Church.

Answer 2

At the time, most rulers were Catholic and believed that the Pope had influence over all of them.  And to top all of that, Roman Catholicism was the only Christian religion at the time.