Why didn't the ghost king rout?

[FrankTrollman]

Units can, unfortunately, escape from a siege if they own an adjacent province.

However, a commander in a castle never runs away because of losing all the troops under his command. If it makes you feel better, consider that the Ghost King still has troops under his command - the castle archers. You can't attack them, and you can't interact with them, but they are there. And they never run.

Note that troops will run away like little girls if they have no commanders. It's just that the other way will never happen.

-Frank