It’s likely of course that Disney never had any intention of continuing the stories of the Rogue One cast after the standalone movie, regardless of the movie’s ultimate box office performance.
It might have been cool to watch that cast come together again for another side-adventure set during a later major battle in the Star Wars universe.
As such, from the studio’s point-of-view, summarily annihilating all those characters was no big deal.
For a company as focused on maximizing assets as Disney, wiping out the cast of a potential new franchise in one fell swoop almost feels like a daring move.