He was the first person to have an autobiography published during his lifetime
Italians adored Michelangelo both in his lifetime and afterward, either in spite of or perhaps even because of his fascinating nature. Everyone was curious about "Il Divino," or the Divine, and everyone desired a colorful account of his life's events. This is perhaps what inspired Michelangelo to write two full-length autobiographies during his lifetime, instead of just one.
In actuality, compared to other artists from his era, Michelangelo's beliefs, life, and work are far better understood. In addition to his autobiographies, there are several records from the government or papal bureaucracy that have survived through the years, as well as letters and diaries from persons who interacted with the artist and artists who respected him. Each of the numerous government or papal projects that Michelangelo was hired to complete was thoroughly documented and archived, providing us with information on his work, schedule, and compensation during his lifetime.