Celestia despite tricking her was right... Maybe she could give a little humble work back for her subjects. Even if she failed, so many ponies from all across Equestria came in droves to either audition for this, or to see the play itself. And in part it was because they heard Celestia was going to perform; which turned out to be a ruse... But now a different princess was filling that role, and that seemed to be still generating a lot of energy in the theater. So maybe it wasn't a total ruse.