Lucy seems to have faith in Charlie Brown's ability to direct the Christmas play, given how she seems surprised to hear that not everyone shares her enthusiasm for his potential. She also, for the most part, happily helps him out.
Let's be honest: The last 5 minutes are nothing but CMOH. And really, Charlie Brown needed it.
Lucy: Charlie Brown is a blockhead, but he did get a nice tree.
To say nothing of Linus's sermon.
He lets go of his blanket when he reaches "Fear not!" Awesome and heartwarming at the same time.
The sermon makes everybody realize that Charlie Brown was actually right on the ball by choosing that tree.
"I never thought it was such a bad little tree. It's not bad at all, really. Maybe it just needs a little love..."
"MERRY CHRISTMAS, CHARLIE BROWN!"
When the entire cast sings "Hark the Herald Angels Sing" while standing around the little Christmas tree, now beautifully decorated and standing upright.