The vast majority of the artists on "The Hamilton Mixtape" were at their peak-charting success ten years ago.
(An odd exception for Sia, who has had one of the longest and strangely upside-down chart performances of anyone in the last two decades, and I suppose John Legend, who only squeaked out his first #1 hit in 2014, but was certainly a 'hotter star' in 2004.) A few of them are up-n-comers, like Chance the Rapper. That was a good get. Dude won the Best New Artist Grammy last year. But his cover of "Dear Theodosia" was clearly intended as a kind of mellow post-script, not a potential chart-topping hit.
Most of the covers are fine. And dull. Like Usher's "Wait for It." It's forgettable, inoffensive, and blah. But if it had been recorded by Drake, Future or The Weeknd, it MIGHT have actually reached the pop charts.
Pop stars record theater music at the "Love Boat" / "Hollywood Squares" portions of their careers. When they're looking for new things to do to stay in the national imagination.
I do think the material itself might be a big reason why. Idina herself couldn't get her pop recording "Defying Gravity" to crack the charts here.
But I have heard it in coffeehouses in South America. So there's that.