The real answer is that musical storytelling arguably predates spoken storytelling and that translates easily to the stage in any culture with a tradition of stagework, because singing allows the conveyance of more complex and nuanced emotional information to the audience, but that's no fun and why not take the badpost seriously.
So, Western Musicals have their origin in the Upper Class Masques (a music and dance entertainment, kind of like if a rave was crossed with a themed concept album and everyone in the castle dressed up and danced and sang the songs in the correct sequence together) of the late 1500s.
One day, a group of composers in Florence and nearby cities had a hardon for a massive misinterpretation of what Greek theatre was. They got together and said "hey, the Greeks talk a lot about how music is used in their plays as commentary, what if we like, made a masque that attempted to mimic this and made the narrators sing like a Greek chorus and the participants (who were usually drunk nobles) speak instead of dance!?
This failed spectacularly, but resulted in first semi Operas (an art form that stuck around longer in Britain) and eventually, once they realised the soloist work could benefit from both song and professional singing, in Dafne, the first opera. This sucked, but after a decade or so a guy named Monteverdi managed to make it suck less and created L'Orfeo, the first Opera still performed today. It has Soloists, Chorus, Asides, Duets, and all the action is staged in real time.
Opera matured, and the first true Comic opera was made in the 1610s-20s, probably by Francesca Caccini, a daughter of one of the original group and chief composer of the Medici court. Comic opera quickly dropped classicism and became more and more character-driven and realistic.
Later, around 1700, the Low Pastoral and the related Ballad Opera developed in England. The Low Pastoral is an operatic work that features real humans in a rural setting, and has many of the standard musical conventions of boy meets girl, loses girl, gets her back, kiss as curtain closes etc. The Ballad Opera often uses spoken words, is often downright cynical and offensive in plot structure, and steals its tunes from local folk songs and sometimes popular opera arias of the time, basically a jukebox musical. One of these, the Beggars Opera is considered to be the first proto musical for this reason, is still popular today, and Brecht rewrote and scored it as the Threepenny Opera.
During the 19th century, these two forms merged with Comic Opera and other forms like Singspiel into the wildly popular Operetta, first by Offenbach and then, most famously, by Gilbert and Sullivan (whose fault this all is). G&S operettas contain all the forms of a modern musical save that they're much harder to sing and have less dance. Luckily, the collapse of the common practice period around 1900 meant that simpler tunes and massive dance numbers of the new early jazz dances were popular, resulting in Edwardian Musical Comedy. Eventually they learned how to compose decent songs again, and Kern and Hammerstien incorporated African American musical traditions to create Showboat, the first true modern musical.
So that's why musicals are a thing and who you have to go back in time and kill to stop them.
The real answer is that musical storytelling arguably predates spoken storytelling and that translates easily to the stage in any culture with a tradition of stagework, because singing allows the conveyance of more complex and nuanced emotional information to the audience, but that's no fun and why not take the badpost seriously.
So, Western Musicals have their origin in the Upper Class Masques (a music and dance entertainment, kind of like if a rave was crossed with a themed concept album and everyone in the castle dressed up and danced and sang the songs in the correct sequence together) of the late 1500s.
One day, a group of composers in Florence and nearby cities had a hardon for a massive misinterpretation of what Greek theatre was. They got together and said "hey, the Greeks talk a lot about how music is used in their plays as commentary, what if we like, made a masque that attempted to mimic this and made the narrators sing like a Greek chorus and the participants (who were usually drunk nobles) speak instead of dance!?
This failed spectacularly, but resulted in first semi Operas (an art form that stuck around longer in Britain) and eventually, once they realised the soloist work could benefit from both song and professional singing, in Dafne, the first opera. This sucked, but after a decade or so a guy named Monteverdi managed to make it suck less and created L'Orfeo, the first Opera still performed today. It has Soloists, Chorus, Asides, Duets, and all the action is staged in real time.
Opera matured, and the first true Comic opera was made in the 1610s-20s, probably by Francesca Caccini, a daughter of one of the original group and chief composer of the Medici court. Comic opera quickly dropped classicism and became more and more character-driven and realistic.
Later, around 1700, the Low Pastoral and the related Ballad Opera developed in England. The Low Pastoral is an operatic work that features real humans in a rural setting, and has many of the standard musical conventions of boy meets girl, loses girl, gets her back, kiss as curtain closes etc. The Ballad Opera often uses spoken words, is often downright cynical and offensive in plot structure, and steals its tunes from local folk songs and sometimes popular opera arias of the time, basically a jukebox musical. One of these, the Beggars Opera is considered to be the first proto musical for this reason, is still popular today, and Brecht rewrote and scored it as the Threepenny Opera.
During the 19th century, these two forms merged with Comic Opera and other forms like Singspiel into the wildly popular Operetta, first by Offenbach and then, most famously, by Gilbert and Sullivan (whose fault this all is). G&S operettas contain all the forms of a modern musical save that they're much harder to sing and have less dance. Luckily, the collapse of the common practice period around 1900 meant that simpler tunes and massive dance numbers of the new early jazz dances were popular, resulting in Edwardian Musical Comedy. Eventually they learned how to compose decent songs again, and Kern and Hammerstien incorporated African American musical traditions to create Showboat, the first true modern musical.
So that's why musicals are a thing and who you have to go back in time and kill to stop them.