Why was Rui Faleiro unable to sail with Ferdinand Magellan in 1519?

Rui Faleiro, a Portuguese cosmographer who was originally appointed as a joint captain general alongside Ferdinand Magellan, was unable to sail with the 1519 expedition due to his mental instability.1

While Magellan and Faleiro had successfully secured royal assent from King Charles I to seek a westward route to the Spice Islands, the expedition faced numerous organizational challenges, including opposition from Spanish officials and interference from the Portuguese crown. Ultimately, Faleiro’s condition prevented him from participating in the voyage, leaving Magellan to lead the fleet as it departed from Sanlúcar de Barrameda on September 20, 1519.1