Who persuaded Giuseppe Verdi to return to opera after his retirement?

Giuseppe Verdi’s return to the world of opera after his retirement was primarily due to the initiative of his publisher, Giulio Ricordi.1

Reluctant to see his most successful composer stop working, Ricordi orchestrated a reconciliation between Verdi and the writer and composer Arrigo Boito, who had previously offended the maestro with youthful criticism. Ricordi proposed that Boito write a libretto based on William Shakespeare’s Othello, which successfully piqued Verdi's interest. As a test of their collaboration, Boito revised the libretto for Simon Boccanegra, leading to the eventual creation of the masterpiece Otello.1

Later, Ricordi and Boito successfully intervened once more to persuade the aging composer to create his final operatic work, Falstaff, which was based on Shakespeare's The Merry Wives of Windsor.1