fuller entry in Italian Wikipedia: "Vivaldi composed this work in a period when opera was subject to a profound evolution. In 1720, after having released himself from the duties that had tied him to the "post-Gonzaga" court in Mantua, where he had been active for over a year, he returned to his native Venice. There, he became a victim of a conservative faction led by Benedetto Marcello, and was sidelined from the Teatro Sant'Angelo, where his previous works had been performed. It was due to the hostile environment in Venice that Vivaldi decided in 1721 to accept the commission to compose and stage a new opera for Milan." Note however that cast list given in Italian Wikipedia appears different.
