[wolverine876]

> It's comparatively easy to say that with hindsight.

Yes, and I omitted an essential factor: All the funded projects that failed and are mostly forgotten.

> There was about as much reason in 1940 to predict that making a nuclear bomb was feasible with enough resources as there is today to think the same about fusion power generation.

My impression is that it was believed to be a very likely project, and mostly a race with the Nazis. An excerpt from Einstein's letter to FDR, credited with kicking off the project:

In the course of the last four months it has been made probable—through the work of Joliot in France as well as Fermi and Szilard in America—that it may become possible to set up a nuclear chain reaction in a large mass of uranium by which vast amounts of power and large quantities of new radium-like elements would be generated. Now it appears almost certain that this could be achieved in the immediate future.

This phenomenon would also lead to the construction of bombs, and it is conceivable—though much less certain—that extremely powerful bombs of a new type may thus be constructed.

https://www.atomicheritage.org/key-documents/einstein-szilar...