This one couldn't be easier, folks. The title refers to the nickname of the main character, John "Crash" Coogan, so named because he's super into football.
Also, on a personal level, he's a bit of a disaster—rude, hyper, and prone to violent hissy fits. "Disaster" isn't much of a nickname, though. It just doesn't have the same ring to it, you know?
Now, if you're really in the mood to get existential, we could dig a little deeper and say that poor Crash's life came crashing down after his grandfather's stroke.
(Get it? Crash? Yeah, you get it.)
See, aging and illness make us think about death, and thinking about death makes us want to be better people. At least, that's the hope. As the book progresses, we see Crash reconsider how he makes his way through the world. Instead of seeking out conflicts all the time, he learns how to play nice.