Honestly there are a lot of operas that take themselves much less seriously than musical theatre. There's a huge difference between the wearing earnestness of Hamilton and, say, 1625's La liberazione di Ruggiero dall'isola d'Alcina which has a chorus mostly comprising of men turned into plants constantly snarking about the action and has the Heroine literally ride in on a dolphin.
I would assume that they're descended from Operas, with the main distinction being how seriously the production takes itself.
Honestly there are a lot of operas that take themselves much less seriously than musical theatre. There's a huge difference between the wearing earnestness of Hamilton and, say, 1625's La liberazione di Ruggiero dall'isola d'Alcina which has a chorus mostly comprising of men turned into plants constantly snarking about the action and has the Heroine literally ride in on a dolphin.
Hmm good point. I'm an absolute philistine who's favorite operas are the ones from Bugs Bunny.