I guess you’re right, PlotHole. Celestia never got stuck in a cage like Twilight, Songbird Serenade, The CMC, Clear Skies and many other ponies captured by the Storm King and his army that were caged because she was petrified alongside her sister Luna and Cadance who was the second Crystal Princess being turned into a statue (the first bring Amore). The Storm King’s ships look way too big. And Canterlot didn’t burn like that. Well, even though the usurper, the Storm King, have created a big storm that could ravage Equestria, I believe that lightning splat and sent fire in some parts of Equestria including Canterlot cause the fire to appear and spread across the kingdom (à la “The Lion King”) before they’re extinguished offscreen when the storm died down by Teilght using the Staff of Sacanas.

Well, because the Storm king create rain, thunder, wind, and lighting bolts, I bet some of them splat in Canterlot and cause some flames and fire the spread some parts of Equestria including Canterlot offscreen.