This is probably a naive question. Maybe someone can answer it quickly for me.
The Manhattan Project started in 1942 and in 1945 the United States detonated three nuclear bombs, including an enriched uranium bomb and a plutonium bomb.
Fast forward sixty years: The Iranians have been allegedly working for several years on developing a nuclear bomb but are, by some projections, still years away from being able to produce one (leaving aside the ability to deliver it).
What is going on here?