Aren't you implying, intentionally or not, that a "Manhattan Project" level of expenditure, $25 billion, is enough to make meaningful progress towards commercial fusion energy production? I don't think that is a given.
According to David Edgerton's The Shock of the Old, Brigadier-General Leslie Groves had previously overseen the construction of several munitions plants costing much more than the entire cost of the Manhattan Engineering District project.
1. Chapter 8, "Invention", p198 in my paperback edition.