Final answer:
Two events led to the end of the increasing prosperity of the High Middle Ages: the outbreak of the Black Death and a series of catastrophes in the 14th century.
Step-by-step explanation:
Two events led to the end of the increasing prosperity of the High Middle Ages. The first event was the outbreak of the Black Death, which occurred between 1347 and 1350 and killed approximately a third of the European population. This devastating plague caused a significant decline in population and disrupted trade and economic activities.
The second event was the series of catastrophes in the 14th century, including the Hundred Years' War, famines, and other epidemics. These calamities caused a recession in the European economy, depleting the wealth of the nobility and the Church. Additionally, the rising prominence of the merchant class and the growing centralization of monarchical power gradually eroded the privileges of the landed elites, leading to the foundation of centralized modern nation-states.