Background: Tosca (Italian pronunciation: ['toska; 'toska]) is an opera in three acts by Giacomo Puccini to an Italian libretto by Luigi Illica and Giuseppe Giacosa. It premiered at the Teatro Costanzi in Rome on 14 January 1900. The work, based on Victorien Sardou's 1887 French-language dramatic play, La Tosca, is a melodramatic piece set in Rome in June 1800, with the Kingdom of Naples's control of Rome threatened by Napoleon's invasion of Italy. It contains depictions of torture, murder and suicide, as well as some of Puccini's best-known lyrical arias.
Context: The French playwright Victorien Sardou wrote more than 70 plays, almost all of them successful, and none of them performed today. In the early 1880s Sardou began a collaboration with actress Sarah Bernhardt, whom he provided with a series of historical melodramas. His third Bernhardt play, La Tosca, which premiered in Paris on 24 November 1887, and in which she starred throughout Europe, was an outstanding success, with more than 3,000 performances in France alone.  Puccini had seen La Tosca at least twice, in Milan and Turin. On 7 May 1889 he wrote to his publisher, Giulio Ricordi, begging him to get Sardou's permission for the work to be made into an opera: "I see in this Tosca the opera I need, with no overblown proportions, no elaborate spectacle, nor will it call for the usual excessive amount of music."  Ricordi sent his agent in Paris, Emanuele Muzio, to negotiate with Sardou, who preferred that his play be adapted by a French composer. He complained about the reception La Tosca had received in Italy, particularly in Milan, and warned that other composers were interested in the piece. Nonetheless, Ricordi reached terms with Sardou and assigned the librettist Luigi Illica to write a scenario for an adaptation.  In 1891, Illica advised Puccini against the project, most likely because he felt the play could not be successfully adapted to a musical form. When Sardou expressed his unease at entrusting his most successful work to a relatively new composer whose music he did not like, Puccini took offence. He withdrew from the agreement, which Ricordi then assigned to the composer Alberto Franchetti. Illica wrote a libretto for Franchetti, who was never at ease with the assignment.  When Puccini once again became interested in Tosca, Ricordi was able to get Franchetti to surrender the rights so he could recommission Puccini. One story relates that Ricordi convinced Franchetti that the work was too violent to be successfully staged. A Franchetti family tradition holds that Franchetti gave the work back as a grand gesture, saying, "He has more talent than I do." American scholar Deborah Burton contends that Franchetti gave it up simply because he saw little merit in it and could not feel the music in the play. Whatever the reason, Franchetti surrendered the rights in May 1895, and in August Puccini signed a contract to resume control of the project.
Question: What made it so popular?

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