What made Lee Kuan Yew a great leader? Lee Kuan Yew governed Singapore for three decades(1959-1990) becoming the longest-serving Prime Minister in history. Lee Kuan Yew transformed Singapore's economy from largely agricultural to one of the strongest industrial societies in the world. Under the leadership of Lee Kuan Yew. Singapore became one of the safest countries in the world thanks to use of corporal and capital punishment.