Final answer:
Jim Tressel was the head coach of the Ohio State Buckeyes during their 2002 national championship victory in the Fiesta Bowl.
Step-by-step explanation:
The coach of the Ohio State Buckeyes when they won the national championship in 2002 was Jim Tressel. The Buckeyes were victorious in the Fiesta Bowl, claiming the BCS National Championship under his leadership.
With a focus on discipline and fundamentals, Tressel brought the Buckeye's football program its first national title since 1968, marking a significant achievement in Ohio State football history.