Star Wars has painted itself into a corner with the Mandoverse. Though Thrawn’s introduction in Ahsoka established a major new threat, he can’t actually wreak that much havoc. We already know the New Republic survives until decades later, when it eventually falls to the First Order, so the status quo can’t really change.
But what seemed like a plot hole in the sequel trilogy could actually be the result of Thrawn’s evil ways — and could also be a clue to the upcoming Star Wars movie written and directed by Mandoverse overseer Dave Filoni.
Redditor Shawn_S0L0 suggests this movie will feature a huge attack by Thrawn on Coruscant, which is presumably still the capital of the New Republic. That would increase the scope of the Mandoverse from a group of side characters snuffing out threats like Moff Gideon to a villain who throws the entire fate of the Republic into question. Granted, we already know the answer to that question thanks to the sequel trilogy, but it would be exciting nonetheless.
This would explain why Coruscant is nowhere to be seen in the sequel trilogy, with the New Order using Starkiller Base in The Force Awakens to blast some random planets like Hosnian Prime instead. Canonically, this oddity is later explained away by revealing that the New Republic eschewed Coruscant as its capital, instead hopping from planet to planet like an itinerant court of old. But it’s not explained why the Senate moved around; maybe they had to wait while Coruscant was rebuilt after an attack by Thrawn we’ve yet to see?
This would actually echo what happened in the non-canon Legends timeline. In the New Jedi Order series, the New Republic capital of Coruscant is taken over by the invading Yuuhzhan Vong, who destroy the bustling metropolis planet. They agree to rebuild it after they surrender, but it’s a long process.
Thrawn may be one of the biggest villains of the old Extended Universe, but now he’s trying to carve out a space in a modern canon almost entirely occupied by Palpatine in his various forms. But Thrawn is terrifying in his own way, and finding a plan that rocks the Republic without harming Star Wars’ sacred timeline is exactly what a master tactician like him would do.