Final answer:
Pope Leo X decided to excommunicate Martin Luther due to his challenge to the Catholic Church's practices, particularly the sale of indulgences, leading to the Protestant Reformation. This was a response to protect the Church's authority. Earlier, the pope's decision via the Treaty of Tordesillas influenced the linguistic landscape of South and Central America.
Step-by-step explanation:
Pope Leo X, known for his role in the Protestant Reformation, decided to excommunicate Martin Luther in 1521. Luther had challenged the Catholic Church's practices, such as the sale of indulgences, which Pope Leo X had authorized to finance the reconstruction of St. Peter's Basilica.
In spite of possible attempts by Luther to be somewhat conciliatory, his bold propositions, especially the Ninety-five Theses, were seen as a direct challenge to the authority of the Church and the Pope. Therefore, Leo X's decision to excommunicate Luther was primarily a response to what he perceived as an insurmountable challenge to the church's authority and teachings. This pivotal decision contributed significantly to the ensuing Protestant Reformation.
Previously, to prevent conflict between Spain and Portugal over newly discovered lands, the Catholic Pope had arranged the Treaty of Tordesillas, which divided the non-European world between them. This had a profound impact on the languages spoken in South and Central America, such as Portuguese becoming the official language of Brazil, while Spanish spread to most other countries in the region.