Why did Giuseppe Verdi never complete his planned opera based on King Lear?

Giuseppe Verdi held a lifelong fascination with the works of William Shakespeare, whom he famously described as the great searcher of the human heart. Although he considered adapting King Lear as early as the 1840s and remained interested in the project until the end of his life, he never completed the opera.12

The primary obstacles to the project were practical: in 1856 and 1857, when Verdi was prepared to begin work on Re Lear, he was unable to reach an agreement with a theater or secure a cast of singers that he found satisfactory. Consequently, he shifted his focus to other projects, such as Un ballo in maschera, which he was able to complete more readily. While he successfully adapted other Shakespearean themes into masterpieces like Macbeth, Otello, and Falstaff, King Lear remained an unrealized ambition.1