Supposedly the opsec at the Manhattan Project was so good, significant portions of the workforce had no idea on what they were laboring. Post war interviews thought the facility was all a sham, dedicated to nothing but medical testing.
Isn’t this exactly what should be looked into? Find weak point and hit them. Germanys ball bearing plants and oil refineries got targeted this way.
Similar if the Axis had large-scale resistance forces operating in America, able to sustain at-scale acts of industrial sabotage.
But the Axis already knew that America had a huge copper industry. With no way to affect that industry, at scale - long lists of American copper mines, refining facilities, factories, etc. were no more valuable to the Axis than collections of apple pie recipes.
The oil campaign OTOH, worked out well.
I'd guess actually going after stuff like wire/brass casing production, while it could have an impact, the 'ROI' is likely lower than more important logistics meta-targets (i.e. oil and gas production and transport infra/equip) and those are far easier to 're-boot-strap', one can theoretically draw copper wire from their garage with a reasonable base starting piece and draw jig/rig.
Also, like bearings, it's easier to 'surplus'. Surplus Oil sitting in a field or penetrable location? Obvious easy pickings. Stockpiled wire? I mean you could but frankly even if you burned/melted all the wires someone can just collect it and re-make wire. It's not like oil where the resource gets completely destroyed in the process.
(Ammo depots, OTOH, would make sense.)
Worth noting (unless someone else already did) that the UK program that technically started before the Manhattan Project was called 'Tube Alloys'.
Think about it, cobalt is too slow. Polonium is ideal - you need a much smaller amount, and in five years it's gone, ten years, it's undetectable. Except that it decays into a specific isotope of lead, which could raise some questions, but you call it a toxin, and hope that the evidence gets destroyed in the process...