We still don’t know what conclusion the Roger pirates made when they decided not to fight Imu or why all these specific occurrences (Shirahoshi, Pluton, Nika, Galleila) are all necessary. At first people assumed it was because Imu was just that powerful, but at this time he seems like the strongest in the verse but not to the extent that Madara was compared to the Kage.
So there may just be other forces at play we just don’t know
So there may just be other forces at play we just don’t know