To try and explain why I think this line is so bad, let’s compare it to Return of the Jedi, which introduces in the opening crawl that somehow, the Death Star has returned. Granted, it strains credulity much less to believe that the Empire would rebuild the Death Star, but it’s still a hamfisted way of giving the final movie in the trilogy an instantly recognizable threat.

So how does ROTJ deal with this awkward plot device? By letting the crawl do all the heavy lifting. By the time we get to the briefing scene with Mon Mothma, nobody is questioning how the Empire managed to build a much larger Death Star than the first in a fraction of the time, they are too busy working on how to blow it up. Imagine if instead Han Solo learned of the new Death Star in the rebel briefing and he started asking questions. Maybe this could work if the writers really wanted to explain exactly how the new Death Star was built, but if the writers don’t have an answer, then Han Solo’s question would do nothing except draw attention to the fact that the writers don’t seem to have any idea either. It would go a long way to destroying the audience’s suspension of disbelief in the movie itself.

Thus, one reason why ‘Somehow, Palpatine returned’ is so bad is because it shines a spotlight on the movie’s weakest part, and in so doing lays bare the falseness of the entire narrative.

I think that this line is in large part a self-inflicted wound, since Rise of Skywalker could have taken the Return of the Jedi route and simply established Palpatine’s return off screen, as it had already done. Then the Resistance could behave in a way that illustrates that everyone believes that Palpatine has returned, regardless of the reason, and now the audience is swept up in the quest to destroy him instead of questioning his entire existence.