He showed he could run for power, speed, and that his passing game attributes were solid.
Since he had nothing left to prove, it only makes sense to go pro early, especially given that running backs have the shortest shelf lives in the NFL.
I doubt he would have helped his draft standing by staying for his senior year. The NFL teams prefer that running backs have lower mileage on their tires, especially seeing how Ron Dayne turned out (very heavy workload in college for all 4 years).
The running back stable for 2024 looks to be deep and talented, and with two very talented freshmen, we're in great shape.