I have always thought that some made it off,the torpedo had to have moved fast enough for the fighter to get away.
Same goes with the Executor,some must have gotten off the ship,but not Piet,he implodes
,it was a long way away from the death star and most of the ship was undamaged.
Death Star 2 had people jumping ship left and right,and on DSI,why were all those troopers and officers running around?Patrols,or evacuations?
And I think that DSII was an easy shot,there is no way that all the crews were trained by the time of the attack.