Why is it canonical?

Not to be outdone by its neighbors, and certainly possessing the necessary wealth, Venice hired Donatello to create a monumental statue in honor of the recently deceased general and military hero Erasmo da Narni, or Gattamelata. Erected in Padua, neighbor to Venice and at the time under the control of the Venetian military, the statue draws on a long tradition of depicting military leaders on horseback.