Crabbe is the second of Draco's two huge hangers-on. He doesn't seem to have any more smarts, initiative, or drive than his buddy Goyle has. They both do whatever Draco tells them to do, which makes them excellent henchmen for Malfoy but also kind of hard to understand as characters. Crabbe's father, like Goyle's, is a Death Eater, so presumably this encourages Crabbe's resentment of Harry and all that he stands for. But neither Crabbe nor Goyle is in any way three dimensional at this point of the series: they're just the guys who back Draco whenever he spars with Ron, Hermione, and Harry. What they think or feel (if they think and feel) is totally unavailable to the reader.