Hmm I think they did care some about the spirit cause they showed that in the first film. I think in film two, the director was keeping fairly true to the book for the first 35 minutes.
Caspian escapes Miraz's castle after Dr. Corneilus wakes him and says Prunaprismia has had a son. He runs into the Narnians and blows the horn. He then becomes leader of the Narnians in their attempt to stop Miraz. The Pevensies do the exact same thing, explore the ruins, meet Trumpkin, try to find Caspian, get stuck at the Gorge where Lucy claims to see Aslan, the others don't believe her, they go a different route and get in trouble, they go back and find a safe way down. While the others are sleeping Lucy leaves and finds Aslan herself.....
then things go cur-fluie once we realize that it was only a dream.
Caspian attacks Peter, a bad start to a uh...friendship....Peter suggests the Night Raid, Caspian abandons the plan and rescues the doctor and awakens Miraz, the whole thing gets messed up and several Narnians die. Then Peter and Caspian get angry at each other. Then Nikabrik and co. actually begin to resurect the White Witch and Pete and Caspian almost agree with it....thankfully Ed saves the day. Peter and Caspian make amends, Susan and Caspian start fliriting, and Peter and Miraz have a fight to the death duel. Lucy rides to "the Darkest Parts of the forest" with susan, but they get attacked and Susan acts like some warrior Queen and kills 10 soldiers...but then a soldier nearly kills her...untill she is rescued by Caspian(I almost thought she would say "Oh my Hero!"). Peter wins the duel, but Sopesian kills Miraz and blames the Narnians for treachery and a huge fight begins. FINNALLY LUCY FINDS ASLAN AND HE SHOWS UP!!! Aslan wakes the trees and the river god to win the battle and everyone parties at the end. Then Susan kisses Caspian good bye, and the kiss is followed by a pop song.
So really once they connected the two stories at an earlier point in the film, the entire flow of the story changed.