Eli5: Why is it so hard for a country to make a nuclear bomb?

Question

I’m assuming the science of making one is out there. Why then countries like Iran who so want to develop atomic weapons haven’t been able to do so?

In: Physics

Answer 1

Okay so you know how sometimes you watch a YouTube video showing you exactly how to tie a tie but you still duck up?

Now imagine you have a paper box full of books explaining how to manufacture a nuclear bomb.