Why was Alessandro de’ Medici assassinated in 1537?

Alessandro de’ Medici, the first Duke of Florence, was assassinated on the night of January 5–6, 1537, by his distant cousin, Lorenzino de’ Medici.

Lorenzino, who had been a close companion and partner in the duke's licentious lifestyle, exploited Alessandro’s trust to lure him to his lodging under the pretense of a rendezvous. Once the duke fell asleep, Lorenzino and an accomplice, Scoronconcolo, murdered him after a violent struggle.12

Regarding his motivation, Lorenzino later claimed in his Apologia that he was driven by a love of liberty and a desire to end what he viewed as a tyrannical government, positioning himself as a modern-day Brutus. However, he was ultimately disappointed when his actions failed to spark a popular uprising against the Medici regime in Florence. Following the assassination, the elder branch of the Medici family became extinct, leading to the rise of the younger branch and the eventual establishment of the grand duchy of Tuscany under Cosimo I.213