Across Africa, a number of major dam projects have been resurrected, often with the backing of the so-called emerging powers. However, many are yet to reach construction and are stuck in the early phases of implementation, with studies ongoing. This paper examines this issue in Tanzania, where eight dam projects were pursued between 2005 and 2017 yet only one reached construction. Beyond the literature on anti-dam activists, there is little analysis of the more technical, financial and policy-making processes that cause such stalling of dam projects. Therefore, this paper focuses on the Brazilian government and two companies, Odebrecht and Queiroz Galvão, as the international enablers of two dams in Tanzania, the Stiegler's Gorge and Mnyera projects. It demonstrates the significance of two drivers in undermining these dams construction. One was the inconsistency resulting from Brazil's heavily presidential foreign policy that oscillated from strong support for Africa relations and infrastructure projects between 2010-2012, to a withdrawal of diplomatic and financial support since. The second driver was the degree to which Brazilian governmental and private sector actors misread Tanzanian politics, not understanding the degree of fragmentation in the ruling party and how this affected policymaking. These two factors help explain why the widespread resurrection of dam projects has not entailed an equal boom in dam construction. Additionally, the paper makes a secondary contribution to understanding the factors behind the collapse in Brazil-Africa relations over the last decade, particularly beyond a core group of Lusophone countries.