“The Imperial March” is arguably the most sinister piece of Star Wars music ever composed.
Even after the first Death Star is destroyed, the Empire will continue to hunt the Rebels down, and only when the second Death Star is destroyed during Return of the Jedi will the Imperial forces will permanently fracture.
To have “Hope” resemble the March was a clever way to both foreshadow coming peril without taking away from Rogue One’s victory.
Of course, then that will pave the way for The First Order years later, but that’s a problem for another time.