A character's wants and needs drive the plot.
Before you argue that plot precedes character development, let's focus on how a character's wants and needs can drive a plot forward.
Today I watched WALL STREET again. I know this probably makes me a sucker since I am also planning on watching the sequel to see where Gordon Gekko picks up once he's a free man. And though I hate explanation as a story element, since I don't see Bud Fox in the character list for the 2010 film, I hope they'll tell us what became of him.
So let's focus on Bud Fox for a moment. What did he want? He wanted to be a powerful player on Wall Street, and he did everything he could to become that player. First he cold called Gekko's office 59 days in a row, trying to score just five minutes with the legend. Then, on May 6th -- Gekko's birthday -- he personally delivered a box of Cuban cigars to him. For his effort, Fox was invited to wait (for three hours!) to finally gain his five minutes with Gekko.
At first Fox acted like I might have given the same opportunity - he was tongue tied and nervous. After all, this was WHO Fox wanted to be. Or at least who he wanted to mentor him. But by the end of the five minutes, Fox makes a decision: he divulges insider trading information for the chance to work with Gekko, while at the same time selling a piece of his soul.
And it works.
Fox continues to drive the plot forward by chasing his wants and dreams, even though more pieces of him are dying off in the process. But it isn't until his actions nearly cause massive destruction to his father and his father's friends and co-workers, that Fox realizes he's chasing the wrong dreams. And so the third act becomes about him seeking his redemption.
Do we care? I think we do. We might not agree with all the choices Fox makes, but we empathize with his reasons, and understand that for him, this really is a do-or-die goal. But I'll also admit I am happy redemption seeps in at the end--that Fox ultimately turns out to be his father's son and not a Gekko II. Whether or not you enjoyed the 1987 movie, or liked the characters, you can see how the character's single-minded wants drive the story forward. It's an unstoppable train that carries the viewer on a ride.
Next time we'll look at the equal and opposite viewpoint of the antagonist who works against the protagonist to cause conflict, raise tension, and keep our attention.