Not hard at all. People are questioned, they lie, they trip over their own lies, they crumble. Others have accomplices that give them up under pressure and threats from the police. Some brag to their friends/sweethearts, who have their own agenda, and give them up.
If the asshole keyed couple of cars, the cops would spend very little time on this. Because it's a large damage, they WILL go the extra mile in solving it. This is now a "high profile case" with a large monetary value. Insurance investigators (even more persistent than the local police!), are already questioning everyone.
Trust me,....I've seen it before.