"There is a possibility that Palpatine would attack if they leave," Galahad says. "If something happens that would make it seem that your power is not as secure as the Senators perceive, such as one of your rivals being incited to attack on the pretext of Imperial support or some such nonsense, Palpatine would use that as an excuse to label you all as barbarians and bomb you to smithereens. If all goes well, and nothing notable happens, then Palpatine would have no justifications.
"Still, he is...what he is. There's always the chance that he will throw cares to the wind and bomb Lanzar to smithereens regardless of the success of the mission."
Galahad paces.
"However, if the Senators are still on Lanzar, any bombing or invasions would put their lives at risk. They could die in a bombing. They could be taken hostage. They could be eaten by the dinosaurs in the jungles. Endless numbers of events could befall them. And it would be the Empire's fault.
"So you see, delaying them would be favorable. I do not know enough of what has transpired with your meetings with Andran and the others, so I cannot say how, exactly..."