The officers higher ranked than Vader were all on the Death Star. Subsequently taken to death in the explosion. See what happened was that they wanted coffee. The Death Star was equipped with the top of the line coffee shop. Best EVAR!!! Urns high praise. (Just don't walk in with any life preservers) Anyway the whole chase after the rebels thing happened, they were busy watching a movie in the cineplex, boom death star blew up. They thought they were safe considering they were on a starship that could obliterate an entire planet, all the security personnel around to protect them, and whatnot....

(Stuff I just made up w/out thinking too much about it. Enjoy! )