Hiruzen's responsible for the village surviving.
Tobirama created ninjutsu, attempted peaceful negotiations twice with Kumogakure (died one of those times), IIRC created the Chuunin Exam & ANBU + the police force which resulted in Uchiha discrimination.
Very proactive Hokage but he also had a short tenure. Hiruzen was a youngerster when Hashirama was around and was a teen when Tobirama died. So at most he had a few years to be Hokage, short reign.
Hashirama created the village, big ups. Hashirama handed out bijuu, big downs.