Why was Donatello’s Gattamelata monument controversial when it was commissioned?

The commission of Donatello’s Gattamelata monument was considered scandalous and controversial because it broke with long-standing tradition regarding public honors.1

Historically, the creation of bronze equestrian monuments had been the exclusive prerogative of rulers since the days of the Roman Empire. Because the subject of the statue, Erasmo da Narni (known as Gattamelata), was a condottiere—a leader of mercenary troops—rather than a sovereign ruler, the project was seen as an unprecedented and inappropriate elevation of a private individual to a status previously reserved only for monarchs.1

Despite this initial controversy, the statue became a landmark achievement in Renaissance art, establishing the prototype for all Western equestrian monuments that followed.21