Yup, new fork. Presuming you like your teeth and your hands and wrists and collarbones. And your helmet too.
As to the cause of the crack, it may have been your crash if that impacted the bars and applied force to the stem. It could be adjustment b/c carbon steerers are finnicky. Discovery Channel's Trek racing bikes still all use aluminum steerers, and they're the pros who want the lightest possible bikes that are still safe.
Be really glad you caught this. And inspect other carbon parts regularly.